Quote Originally Posted by Shadow12ogue View Post
If you put ClockWorkMod (CWM) on your phone you can do a Nandroid back up, and with Titanium BackUp you can back up user apps. That way if you hit a boot loop, or something else like that (I had mine hit a boot up shut off, no restart) you just use the back up made PRIOR to trying to install the zip (aka flashing the ROM).
Just to clear something up, rooting and flashing a custom ROM are two different things, and generally the order operations is: root--> install custom recovery (like CWM)--> install custom ROM. Some devices can be flashed with a custom ROM or recovery without rooting the stock firmware first, but generally you root first, install ROM Manger from the market, and flash CWM from there. Making a backup of your unrooted phone is often difficult or impossible, but there will generally be stock images floating around that you can use to return to stock if you want.