also, if your on a custom rom, it may seem so simple, but restart the phone once per day, the phone seems to absolutely love like 1 reboot a day, and since custom roms have better space management, it should clear alot of stuff out
i also every now and again like to go to my applications and view them all and i scroll threw very slow and find ones i forgot i installed and ones i dont use and get them outta there
also while in the applications, anything that doesnt involve a widget, launcher, email or something in the same, can normally be moved to the sd card which saves so much phone space
Also if you use apps like Facebook, you can normally open the app and set it to Never Refresh/Update itself, so the app only uses space and refreshes the page when your actually using it