Steve,
Couldn't agree with Smokey more. Just to expand though, focus on Mathematics and Physics. This will ensure you have a base kowledge for future subjects. Don't specify in one subject and 'burn you bridges'. Leave your mind open and listen to RELIABLE sources. I first got my pilots license, but now really enjoy the engineering side. A sound knowledge of Maths has meant I get to make the decision.
Whatever you do, don't forget to enjoy it. Have fun starting on a career you will enjoy and contribute to, but don't put the blinkers up too early. The world is a very big place, but from a 23 yr old sounds a bit hypocritical. Good luck in whatever you do
Ciao
The Reverand