Depends on the weather, but a nice stroll down the pier is always good. There's a little centre at the end that has a cafe, some old penny type arcade machines and exhibitions about the local wildlife.
There is a train that runs down the pier so if you walk one way and find it a bit too much, you can always get the train back.
Ocean Plaza has got a few good shops and some lovely restaurants. There's the usual chain type ones but the best is Pizzeria Italia - a great find on a windy day!