There are all sorts of theories about how firmly you should grip your club. Most amateurs end up with what I call the "death grip," where it seems like they are trying to strangle the club. That would be a bit too firm.
For full swing, think of an egg ... a raw egg. And watch this video to learn how to select grip pressure that depends on your situation. By the way, correct grip pressure off the tee will do wonders for ending your slice.
Enjoy the game again,