Phone is stuck in bootloop:
This is called a bootloop or soft brick. This has probably happened becasue you did not perform a complete wipe before flashing ROM. It is best to perform a clean installation. To resolve this issue, you have to turn off device by pulling out battery. Now put battery in again and boot into CWM mode. To do so, press and hold Volume Up + Home + Power buttons simultaneously. Once in CWM mode, you have to perform a Factory reset. After you have done factory reset, now navigate to advanced and wipe dalvik cache. The last thing you need to do is to wipe cache partition. After you have done all 3 step explained here, your device will reboot properly. You may also face this issue if you are flashing this custom ROM over another custom ROM already installed. To resolve this issue, you will have to flash stock ROM via Odin PC, then install CWM and then flash the ROM. Otherwise, even if ROM boots up properly, already installed files of previous ROM might conflict with new ROM. The only condition when you can flash a custom ROM over another is when it is an update of already installed ROM. You do not even have to perform a factory reset in this case. However, you have to wipe cache partition and dalvik cache in this case.
Battery percentage is not calibrated:
This problem occurs very often after flashing a custom ROM. This is a minor issue and it can be easily resolved. The best way to resolve this issue is to let the battery fall down to minium. When it is about to be finished, boot ito CWM mode by pressing and holding Volume Up + Home + Power buttons simultaneously. In CWM mode, locate the option called Wipe battery stats. With this option, you will wipe previously stored battery stats information on device. After doing this, do not turn on the device. Just plug it into its AC adapter and leave it for 4 to 5 hours. After you turn it on, not only battery percentage will be calibrated, you will also see and improvement in battery life of your smartphone.
Extreme battery drain:
In this case, follow same steps as explained in above section. If problem still persists, copy all data on your smartphone’s SD Card and internal memory to a PC. Now format internal and external memory of device. Now copy all data back to your device. Also check those apps, which are using too much battery in background. You can monitor background apps using GSam Battery Monitor. You can download it from Play Store. You can freeze such apps using Titanium Backup. It will improve your device’s battery life.
Phone unable to enter Fastboot mode:
Fastboot mode is used to flash .img and .elf files on Android devices. Every device has its own specific method for entering fastboot mode. For your device, visit previous page.
If your device is not entering fastboot mode, you need to install ADB and Fastboot drivers using guide provided in second page. Also install USB drivers specific for your device. If you have PC Companion installed on your PC, you must close it completely in order to avoid problems. Also try different USB ports of your desktop PC or laptop. If your problem is still persisting, ask us in comments below.