Dusk balls are probably the best balls after the master ball. Dusk balls work best at night or in a cave.so what I always do is wait till 8:00 pm or later and catch Pokemon with a dusk ball, which works even better than an ultra ball.
Dusk balls are superb for catching the legendary pokemon. Wait till night and then you can catch dialga(i actually caught dialga with a pokeball. Sweet, huh?) and palkia, gratania, azelf and uxie (mesprit is a find and catch Pokemon so dusk balls are okay but not as effenctive, same with cresselia), heatran, regigigas, androtom.
Hope this helps
Added by: pokelover Sep 29th 2008, ID#9207