First, I think you should go to Sheldon Brown to see what his site has on basics for a flat. But, I'll try to give you some pointers.
1. You need to change the tube for sure. The tube goes flat not the tire.
2. To change the tube you need tire levers that lift the tire over the rim, one side at a time. I'd buy three levers.
3. You need to inspect the tire and the tube to find out if they caused the flat because if they did, you're going to get another flat quickly.
4. It helps if you know where the flat/leak in the tube occurred so that you can trace it to that part of the tire and rim.
5. Inspect the rim, assure that there are no burrs on the alloy, assure that the rim tape is covering all the spoke holes.
6. Inspect the tire, look for something sharp protruding into the tire. Look for small holes that can pinch a tire.
You might want to take it to an LBS and ask to watch them check the tire and rim before they install the new tube, that way you can learn from them.
7. Carry a cell phone, you never know when you need a ride.
I'm sure others will add to this list.