We potty trained my little guy this summer just before he was 2 1/2. We tried several techniques over two days that worked great. After the 2 days he was good to go.
1. sit him on the potty backwards (if he's not standing) and let him pee to hit cheerios
2. they have a potty magnet book at the book store and everytime he peed in the potty we did a potty song and he got to go put a magnet up
3. after a full week of peeing on his own we had a "pee pee in the potty" party at the ice cream store
4. we started by taking him to the potty every 2 hours until he started saying he had to go on his own
5. we got him naked on the first day so he realized what the sensation was - although it looks like you might be beyond that now.
Night time is very hard for children - especially boys. If he's doing great during the day at 3 that's fantastic. Give night time more time. If you've had any big changes - school, move, sibling etc. then that may cause the delay.
just relax and don't push it - he'll follow your lead
good luck