Slum mentioned that he goes from wherever he was when he was last here, but he's here often. And he's really good about back-reading stuff. I do the same on the weekend but when I come back after a few days it really depends. I always go back 5-6 pages so I see what folks have been chatting about, and as much further as I have time. It also gives you the chance to quote a few that you can say something about.
Be sure to give a reaction to things when you like or dislike them. The reactions give coins to the person who posted. And follow the advice Slum provided about reading the first post. It has stuff to help.