I tried The Colour of Magic. I had heard some good things about his books from someone at work so I wanted to get into them.
CoM isn't a good place to start. His early books are not nearly as good as his mid-late stuff.
Try Night Watch, Lords and Ladies or....Feet of Clay, if you want to try his books again. Especially the first, it's my favourite Watch book. I think. Hard to say, actually, they're all pretty good.