This guide assumes you are fully rooted at this point. If not follow any one of the guides in the Wiki that has been stickied on the main page of the Evo Dev forum. My personal recommendation is the Unrevoked. Very easy to use, just read up and make sure your phone is compatible.
To test root type "su" into a terminal. You should get a "#" back. You can use a terminal emulator from the market or ADB. To get ADB up and running follow this guide here. If that seems confusing than take a look at this guide I wrote for Notion Ink Adam Tablet users here. That guide is for Windows users, but Mac and *nix users shouldn't be much more difficult.
Once rooted you can use the app quickboot to boot into recovery to do a NAND backup. If your ROM doesn't have this app installed, download from Marketplace. Open app and choose "Recovery". Once into your recovery use the volume buttons on the side to scroll up and down and power button to select to get to the option to backup. I have clockwork installed so my screen looks different, but you should be able to find the NAND backup option. This will take awhile so be patient.
Once done you can reboot and continue on as normal. This is an essential step (or using Rom Manager below). If you ever screw up something major or you try a new ROM and want to go back, this will allow you to restore easily and get back to a point where things worked fine. It would also be highly recommended to do one of these backups before doing something major that has potential to break things. Use best judgment here.
Even easier than the above is to use Rom Manager. Download it from the marketplace, run it, and let it update your recovery image for you. Once this is done go to the bottom of this app and choose "Backup Current ROM" This should do a full NAND backup. I would recommend buying this app for the other features it has, but it is up to you.
Titanium Backup (TB):
Once you have your NAND backup I would also recommend installing Titanium Backup from the Marketplace (I would also pay for the license because you get better performance and the dev deserves some green for this awesome app!). Once installed open it. The first time it will ask you to update Busybox. Let it and wait for this to download. When done it will ask you reboot app from the notification area. Do this and then wait for app to fully load, two messages should appear, the second one indicates it is fully loaded. Then hit menu and go to the batch section. Choose " Backup all user apps + system data".
This will backup everything on your phone for you to your SD card. This will take a while so go get some coffee and check back in. Do not close the app or turn off your phone, the screen can go blank and you can let it sit, but it will need time to run. I think when the screen turns off it puts an icon in notification that should be updating the progress of the batch. Once done, it should tell you in the notification area. For me it takes awhile with my 228 some elements I'm backing up. Your mileage will vary.
I recently came across a thread that mentions using Handy Backup for backing up SMS/MMS messages. I have not tried this app or used it so I don't have any directions to give on it. But I have had people ask and I have seen folks ask in other threads. So if TB doesn't give you enough, try this one too.
Backup to Computer:
I'm still looking for a better method for this one. I'm sure someone has something and if you do please let me know so I can update this section.
Currently I backup files and folders to my local NAS at home after major changes. Incremental changes I let TB handle. This is just a simple process of setting the SD card to storage and copy/paste. Works fine and I have only done this once so far after everything was set to my liking.
You might wonder why this important? Well if you are going to play around a lot with different ROMs and constantly read/writing info to your SD card, it is important because SD cards are not perfect. They can be corrupted and can fail from too much writing of info. It usually takes a lot of work to get one to the point of failure, but I managed to do it with my HTC Mogul so I can vouch that it can happen.
Important folders on SD card:
This will get all backups performed by clockwork. If you grab the entire clockwork folder then you will get ROM downloads and such too. I don't really recommend this as it never takes more than 25 minutes for me to download any image. Plus with a secure NAND backup, you can always restore quickly.
This should backup the folder used by AmonRa recovery.
Folder used by TB for backing up of apps.
Of course throw in any other folders you deem important. What that is depends on you. Making a backup of everything else probably wont take long too. For me I rarely have more than 7gb of data on my card so backing up takes roughly 30-50 minutes.
All of this may seem like a lot of work, but once done you will have a robust system in place. And will allow you the opportunity to safely play!!
Restoring is a simple process but can be time consuming. To speed things up you can pay for the full version of TB, which I highly recommend.
Follow the directions below for what I do after flashing. If you have already read that and are ready to restore then do the following...
Open up TB and let if fully load, you will get two small popup messages. The second one means that TB has fully loaded the OS information. Then hit the menu key and choose batch. Scroll down and look for "Restore all apps with data". Run this batch to restore everything. Keep in mind if you backed up everything and are now changing ROMs that you might run into problems. I have yet to run across issues, but this is just an FYI. Also another reason to have a full NAND backup with Rom Manager. If you run into too many problems just restore with it and problem solved.
Restores and backups take awhile with TB, but are worth the wait. Once done with the full restore you can then do incremental backup and restores in the future.
Also don't forget to open up the apps after restoring and make sure the apps are setup how you want. Then double check with TB to make sure things are fully backed up, just click "Backup all new apps & newer versions". Once done with this reboot.
After a TB restore always reboot. After the reboot go into Rom Manager and NAND backup following the steps above in the backup section. This will ensure you have a full system backup with the settings you want.
This one is pretty simple. Just open Rom Manager and choose "Manage and Restore Backups". Then choose your backup to restore. If you named the files by date and time you might have to do some guess work, but you should have a rough idea. Once you click the one you want just sit back and wait.
Flashing Tips and Problems
Watch Girls Gone Wild for help with this...
Many people have asked "Why flash custom ROM" or "What are the advantages"? Well I think one of the biggest reasons is performance gain from phone and apps. But for Evo users the number 1 reason should be better battery utilization. This can mean you see same amount of battery life, but with increased phone and app performance, or same performance, but longer battery life.
I think some people might be hesitant because it was one hell of a process rooting their device. Well to those people I say, you are over the mountain now. The hard part is done, flashing is relatively easy. I recommend doing it cause stock can cause some people minor issues and your are missing out on a lot of cool and useful customizations. And if you backup your phone as detailed above, you do not need to worry about losing anything.
Stock ROM with Root (back to defaults) or Completely Unroot:
To flash a stock ROM with root, download one from the wiki of ROMs. Then follow advice in below sections for flashing.
To unroot (This is the "I need to take my phone to Sprint" conundrum...) Follow the wiki link. Or go to HTC's website. Then go to the support section for the HTC Evo. Download the file from them and run it. You will be good to go. And if you followed the backup section above you do not have to worry about anything. Just re-root when you get your new phone or old phone back. And restore.
Also, I recommend taking out your SD card with all the root files on it. No need to bring this up or have to explain things any Sprint tech could easily see. Also if you used Unrevoked Forever you should follow this unroot guide here.
I Just Flashed with no Backups:
Below is what I did before I had Titanium Backup in place and after flashing a custom ROM...
Once booted right after flashing I make sure things look fine, fully sync to Google, then reboot. When I come back from that I turn on WiFi and go to Marketplace and Download section. Any apps I previously downloaded will be in that section waiting for me to download. Download them all at once, DO NOT leave that section before downloading everything, or you will lose that list and it will only show apps currently downloaded and installed.
Once done, open apps and customize to liking. Then download Rom Manager if you don't already have it and follow the above section. Once done with that follow the above section on Titanium Backup. Then enjoy your custom ROM.
Flashing in general:
ALWAYS make sure your battery is at least 50% full. The last thing you want is your phone to die on you in the middle of flashing.
Use Rom Manger and pay for the full version. It is a lot easier and can remove a lot of headaches and problems. If you really want to do it yourself you shouldn't have any problems, this is typically what I do and I haven't run any issues that couldn't be solved yet.
Follow the above backup guides before flashing another custom ROM. Save yourself time and trouble. Also I have read about people using NAND backups to sort of switch between different ROMs. In the short term that shouldn't be a problem, but long term that can make your SD card unstable. Make sure you follow the above section for backing up your SD card to computer.
If changing from one ROM to another it is best practice and almost always recommended to wipe data and dalvik cache. This also will alleviate many issues people run into. And if you follow my backup recommendations then it shouldn't be an issue to do either of these.
If not using Rom Manager, then put the zip of the ROM you want to flash on your SD card, and DO NOT unzip the zip file. Leave it on the root of your SD card as a zip file. Boot into recovery if you are not there already. Find the option to flash from SD card. Then choose the zip file or ROM you want to flash. Wait for everything to flash, then reboot using the option from the recovery menu. Wait for phone to boot. This can take a long time after flashing any new ROM so be patient.
Some ROM devs have other items you can add to their ROM. Follow their directions for flashing those items. Some devs want you to boot first than go back and flash, others allow for you to just start flashing right away with no waiting. Pay attention to the directions on your ROM thread. If you screw something up, try flashing the package again. If things look worse or it didn't work, re-flash your ROM or restore your backup and try again.
Otherwise, flash the ROM following directions above, flash the other packages and themes and items you want, and reboot. All should be well.
Once booted up follow guides above for backing up or restoring. Otherwise if you have problems look below before asking questions. If you can't find it here try searching before asking questions. If you still can't find it feel free to ask for help, but keep the question in the thread for your ROM you are flashing, or if you think it is a rooting issue, in the thread of the root process you followed.
This can be caused by a few things. For one, make sure you wipe data and dalvik cache before flashing a custom ROM. Even if the dev says it is not necessary do this before flashing a new ROM. It can help with these issues. The only exception here is if you are updating to a new version of the same ROM and the dev says there is no reason to wipe in between...
Also you can experience this if you are not fully rooted. Look toward the top of this guide for rooting advice.
Sometimes the ROM can take a while to boot after flashing a new ROM. Be sure you really do have a stuck boot or bootloop before doing a battery pull and troubleshooting. Give it some time to see if it fixes itself. If you are waiting over 30 minutes for something, you probably do have a legit issue.
Exclamation Point with Android Guy Screen
I got this when attempting to upgrade once. To get out of it, battery pull and put battery back in. Hold down "Volume Down Button" and then press power. KEEP HOLDING DOWN volume down button till white screen (Hboot) appears. Release volume down button. Wait for it scan. If it finds your PC file choose no and also no on reboot. NEXT CHANCE YOU GET remove, rename, or move the PC file from the root of your SD card. Choose "Recovery" from menu using volume buttons and power button to select. Once in recovery, choose flash from SD card and choose your ROM.
If you cannot find an image or do not have one, just go back and toggle USB. Then copy paste ROM to SD card. Keep in mind that you might need to wipe data and dalvik cache before flashing as mentioned above.
Another user commented this screen appeared when attempting to go into recovery from Quickboot app. This might mean the recovery image didn't install correctly, or could mean you do not have a recovery image flashed or installed. If this is the case, follow one of the guides in this wiki link to flash a recovery.
If you need to get out of this screen, just do a battery pull. Your ROM should boot up fine.
Battery Issues After Flashing:
Some have claimed issues with battery after flashing. To try recalibrating click here for Cyanogen's guide.
That's all for now!
I'm sure there is plenty more to add to this down the road, but for now this is all the dumping my brain can handle. Leave comments and suggestions and let's make this a strong guide with the right information to help those in need.