You want to flash a custom ROM? You're going to need a solid custom recovery, and the Team Win Recovery Project happens to produce the most popular one out there. Now you can install it on four new devices that, for the most part, have little in common with one another.
Aside from flashing things, TWRP lets you create backups of your device. This is something prudent to do... before flashing your device. Be careful, by the way. Some phones and tablets are tricker to tinker with than others.