wipe your hand on your shorts between points (like in squash, often players even wipe across the wall) and on a towel at change of ends.
go to a pro-shop and buy various different types of overgrip and experiment. maybe you need a perforated one, or find that you like the ones with the lines. it's a very personal choice. Some people are anal and change grips every set, others only after the grip starts to disintegrate.
I use babolat pro-tour as it is what is available regularly at my local shop and it is pretty grippy for me, although I think there are tackier ones.