balancing and sitting on board

I'm just starting to surf. I have tried long boards, funboards and shortboards. obviously, the longoards are the easiest to balance on to paddle and sit, but the funboards and more so the shortboards are pretty difficult. Any suggestions as to where to position yourself in order to paddle fastest and also where on the board should I try to sit when waiting for the waves? I can't seem to quite get it and find myself embarrassing myself by falling off the board.