1. CCleaner. Its really good about cleaning out extraneous temp files from a machine.
As for the Shares...
2. Configure a secondary Drive/Array or SAN and put all your shares on it. That will keep the files off the system drive.
3. If 2 is not an option at this moment, Have a folder on your root level, Call it "shares" and put all shares in it. Makes it easier to monitor them all.
4. Set Hard Quota's on the shares. It will prevent your shares from literally "filling" your drive thus halting printing.
5. Retention Policies. You can write some scripts/scheduled tasks that will purge certain directories on a weekly or specific time duration. Just make sure you notify your users of the policy's and the directories it affects. (and if you're a really nice guy you have it move the files to a "To delete" folder so they have a chance to recover their files.) (If your good you can have it, zip the files as necessary.)
6. Set Notifications, so you're alerted when you drive reaches 75% capacity or whatever is out of the safe zone.
Out of curiosity whats your drive capacity?
For Note 2. you can get an 1TB drive for about $150 these days. I would recommend it.