This is the bee vac that I use. Can not take credit for the design but it is simple to build and works like a charm.
The best advice....
1. Adjust your suction to where the bees are just barely being pulled off of the comb.
2. On hot days pull the sliding lid out and spritz or dribble a little water on them, helps them to keep cool and hydrated.
http://www.youtube.com/watch?v=922gkjV3iqA