You can turn off wi-fi sync, that can cause issues with certain routers. Also there is a reset process that is getting lots of folks good result. Its posted below. I would start there and of course turn off any locations or notifications you dont need or want. Oh and leave it plugged in while you sleep, then its ready to go when you are awake and ready to use it. Wont hurt it to leave it plugged in.
[Credit to Davidch]
i recommend you try my process below with your iPod touch 4th generation. you mention upgrading to iOS 5. if you have not updated to 5.0.1, be sure to do that first. then follow my process step by step and in order.
1. Reset all settings (settings app-> general-> reset)
2 a. Go through initial setup steps (lang, wifi, siri, enable location, etc) and choose setup as new phone (don't worry your apps, data, contacts, mail will still be there). Do NOT restore from iCloud or iTunes (It can copy back corrupt settings)
2 b. If you do not get the complete new setup screen with language setup and setup as new phone or restore from iTune/iCloud backup, be sure to go back to #1 and reset all settings again (it should happen the second time)
3. Turn off system location services timezone and iAd (settings -> location services -> system services)
4. Fully discharge battery (until you get the spinning wheel and it shuts off)
5. Fully recharge battery (overnight if possible)
In my experience this improves the Standby battery drain issue significantly in most cases. It reduces drain from 2-4% or more per hr to 0.5% or less. It has worked for many, many users now. If it does not work after a few try's you may have a real battery or hardware issue and should contact Apple. Good Luck!