The links that Sue has posted are the very best ones. Be sure to order your tickets in advance as that allows you to bypass the gates with the LONG lines and go straight into the center.
We had our rental car and asked for directions at the front desk of the WL, where they gave us a map that was well marked and very easy to follow. The trip quite pleasant and takes 45 minutes to an hour, but the roads are all highways.
By all means, grab one of the bus tours that leave every 15 minutes and sit back and enjoy the guided tour. The Guides are great- I've had them pull over to point out alligators and armadillos
and are very informative. Believe it or not, you can get some great pictures through the bus windows and there are several stops for food, bathrooms and more photo ops.
Take plenty of film or your digital camera and make the huge shop your last stop of the day as there is plenty to buy (but the lines can he very long). Great sale area too!
Make the walking trip up to go into a shuttle (great photo op!) and take a moment to visit the astronaut's memorial for those that have died while training of on missions, It is very moving and, well, there aren't words for me to explain the feelings DD and I had.
It's funny, but I REALLY didn't want to go (who wants to spend a day away from WDW?) but I was glad that I have been there and will continue to make that a regular part of every trip.