Download whatever rom you want (if you like cm10, you should look at Dirty Rom, it's the best cm10 rom)
Download the app Flash GUI app from the play store> open the app, select rom.zip (it'll pop up a dialogue making sure you are unlocked, then another one when you select the zip to make sure you are trying to flash a rom). After hitting "ok" on these pop ups, it will place the zip in the system partition (might take 30 to 60 seconds, sometimes more).. Once it has done that, hit the "flash" button at the bottom of the app, once it is done it will say successful at the bottom of the app, and a pop up will give you reboot options, select reboot to recovery.
Once in recovery, do a factory reset, then install the rom
Also, JellyBam is an amazing hybrid rom-- has cm10-AOKP-ParanoidAndroid all in one... Probably my favorite AOSP rom, and it's just as stable, if not a little more than dirty rom