I disagree about lifting heavy weights, i think it does help, I lift heavy and find that the explosive strength used lifting is a big plus when it comes to manouvers and getting power into your turns, although i do take your point and as this topic is about someone who doesnt surf often big turns arent really what he's aiming for so it probably wouldnt help in this case.
I hear a lot of people talk about yoga and having good results with it for flexibilty, personally i tried it and found it boring but if its your bag then you could find it helps a lot.
If theres a pool near you then use it, if theres one guaranteed thing that will make your time in the sea more productive its being able to paddle stronger and longer without tiring, and swiimming is the key to that. Try and get down there at least twice a week if not 3 times or more.
Maybe buy a longboard (skateboard) to help with your balance, carving a skateboard is similar to a surfboard and requires similar balance.
And watch surf dvds, it may not directly help your surfing but it will keep your stoke up and keep you focused on getting out there, and the guys in the dvds will probably have better style than the guys where you surf so you can hope to pick up some of that
