If you like chocolate, then Cadbury World is a must. It is in Bournville about 15 min on the train from Birmingham New Street. (Bournville itself is a very pleasant village just to wandert around).
I'd agree that a trip on the canal boats is a good idea.
There is also a big wheel outside the International Convention Centre, which is a good way to get to know the city.
I've never been, but the Ikon art gallery is supposed to be interesting.
If you like shopping, then the new Bull Ring is a must. Or for something slightly up market, there are some very nice shops in the mail box.
Just a few ideas to start with. FYI when you are in Birmingham though, the tourist info office is situated just outside Waterstone's on New Street. It's the jaunty looking angular building, sticking out of the middle of the road.