Superuser and Recovery
After gaining access to all the wonderful things associated with superuser capabilities, you'll want to start browsing all the Android forums to find and download a bunch of new custom ROMs to test-drive.
Unfortunately, you can't. Not without the help of a wonderful tool called Recovery. Recovery sits in its own tiny partition in the internal memory of your phone, just as with the phone's original firmware. We'll be using a greatly enhanced version of this recovery partition, giving us access to a plethora of new utilities.
Features of the recovery image include Android backup, adb shell, mount USB storage, advanced update.zip options (ignore asserts and signature checks), and file browser (so you can place your zips in subdirectories and organize them).
There are two major players in the recovery partition game: SPRecovery and ClockworkRecovery. Both of these tools are rock-solid in terms of stability, though Clockwork gives the user more control over the system, with additional tools SPRecovery doesn't have.
ClockworkRecovery is installed extremely easily, as the free (with option to upgrade to an advanced version of the app for $3 or $4) ROM Manager application will install it for you, and help you access backup and install options from within Android.
Here's how to get it working:
Open the Android Market, and search for the ROM Manager application.
Download and install the free version of the app.
Open up ROM Manager, and select "Flash ClockworkMod Recovery," and wait for the download and installation to complete.
Your phone will probably shut down and restart, and you're done!