What do you like doing? The Pavilion is worth a look. There are loads of tiny galleries dotted about. The Lanes are good for antique jewellery and quirky shops. Churchill Square is where your bulk standard high street shops are. There's also the pier!
Terre a Terre does great vegetarian and vegan food, Pho is great for vietnamese food, Chaula's is great for curries. There's Jamie Oliver's restaurant but I've not been there myself but heard good things about it.
The Salt Room on the seafront has great views and food and the Coal Shed. Both local. Chilli pickle voted best uk Indian recently - very authentic I think. I think it might be paddle round the pier this weekend which is fun to watch. Avoid Churchill square- stick to the lanes and the beach if possible.