Now the first thing, I am not going to tell you how to root your phone, because there are already many threads on about it. So I'll be sharing my own experience and the mistakes that I've made; so that you guys, all the newcomers don't do the same mistake and suffer as myself!
Remember always to flash proper kernel with the desired ROM of tours. This is the most important thing!!!! ALWAYS FLASH PROPER KERNEL!!! It is usually included in the ROM zip and named as "boot.img". If you are not S-Off; you have to flash this image using the fastboot commnands in the fastboot usb mode! Always flash this zip othewise your rom will not boot up and cause you troubles.
Now what happened with me(Over a year ago) was; I rooted my one v and was very excited to flash and try new ROMs. At that point of time I didn't study very well about the Kernel thingy and after flashing a Sense Based ROM I tried a CM 9 without flashing proper kernel! And that's it! My device won't boot up and my god I was scared like hell and finally ended up going in the service center; where after almost a month I got a estimate of Rs. 7000 to fix my phone. But in the mean time I studied and gained proper knowledge and obviously I didn't repaired my device at HTC. They returned my device and all I did was flashed the HEllboy kernel and it booted up.
So guys please keep in mind to always flash the proper kernels with your desired roms(If you are not already S-Off).
Thank you guys. Hope this will help a lot of Newbies here.
Remember to hit the thanks button; if this was helpful!