Make sure it's snug (but enough room to stand/turn around in). I use a small cat crate (the airline carrier type). I line the crate w/receiving/baby blankets. She likes to snuggle in them and I found w/her "bed" she can't do that, so the bed is in the living room for rests during the day.
I also have her on my night stand right next to my bed so I can hear her if she whines. The couple times she woke up whining (to pee) I took her out (quietly, no noise and minimal lights) and put her right back in the crate. She kind of scratched at the "door" or the cage but I ignored her, and she went back to sleep.
