Get a high quality lockbox and hang it out your door knob. Keep a copy of your house key in it. This way you won't have to worry about getting locked out of your apartment. You will also be able to give friends/coworkers access to your apartment when you aren't present.

Renter's insurance is good to have whether single or not.

Timers are awesome. I have timers for lamps in my living room and dining room so that they are always on when I get home. Not only is it nice not having to fumble around in the darkness, but the lights are a deterrent to any would-be cat burglars