Using either app, backup everything in you phone into the SD card. Titanium backup will require that you enter batch mode by pressing menu, then running backup everything. MyBackup has a limited 30-days backup, but you'll probably be doing this once only
Step 2: Factory Reset
There's 2 ways of doing it, via Hard button reset, or via internal reset.
Internal reset - Android 2.1
"Settings" > "Privacy" > "Factory data reset"
Internal reset - Android 2.2
"Settings" > "SD & Phone Storage" > "Factory data reset"
Hardware reset
1. Power off your phone (or take out the battery, if it is non-responsive)
2. Holding the [Volume -] key, press the power button once. Hold it until you see three skateboarding Androids at the bottom of the screen
3. Use the Volume buttons to navigate.
4. Select "Bootloader"
5. Select "Clear Storage"
6. Follow the on-screen instructions if you want to factory reset
Step 3: Restore
1. Return to the backup software you used.
2. MyBackup will be easier, but less powerful, so just follow their instructions.
3. Titanium Backup will need to go back to the Batch instructions.