1. Change tavern room doors to only require a key for entry, not exit
If not paying attention it's possible to log into a room that your character doesn't have the key for. Unless the door can be bashed down, there is no way out. Quite unfortunate.
2. Make specific keys for each rooms
Some taverns are quite popular to visit for various reasons. It occasionally happens that a room is occupied, when someone walks in. Having specific keys for each room avoids such an issue.
This is especially important to help alleviate meta-gaming, where e.g. a Paladin is seen conversing with a known Necromancer; the knowledge spreads OOCly, and suddenly bleeds over to IC. Yes, this has happened before. It will happen again.
3. Make tavern room keys persist until server reset
This one is a minor one, and more of a realism one. When buying a key to a room, all the tavern owners state it is a room for the night. Meaning you can come and go as you please. Since keys disappear when entering a tavern through the main door(s) that suspension of disbelief is lost.