The folks over at macminicolo.com have a good guide on setting up a mini to go to a colocation facility. In fact it is good for any mac going to a colocation facility. There are a few additional preferences I think are worth noting.

• Energy Saver - Set the machine to automatically start after a power outage.
• Expose - Set all corners to do nothing (this is the default but if you've changed it it can be bothersome over a remote connection
• CD & DVD - Set all the preferences to ignore. If you have to have a CD inserted remotely you don't want it doing something automatically
• Menu Bar Icons - Remove as much from the menu bar as possible
• Screen Saver - Turn it off. No point in wasting cycles drawing graphics on a non-existent screen