A lot of slow pitch leagues will consider any ball that lands directly behind the plate a strike (as long as it achieved correct height range). Position yourself in a way that lets you hit a ball dropping into that area. Don't worry about it coming over the plate horizontally like it does in fast pitch. I typically stand further back in the box than I would in baseball.
Patience. Because the ball is moving so slowly it's easy to get anxious and swing too soon. Then you're lunging for the ball or chopping up at it. I like to hit it when it's about waist or even knee high. It's more of a golf swing than a baseball swing.
Of course, practice a lot to help get the timing down.