If the car has been sitting for sometime you may have carbon lock. Assuming the battery and the starter are good, you need to remove the spark plugs and squirt ALOT of WD-40 into the rotor housings. Let it soak for a few hours, then with the car in 4th gear, FIRMLY rock the car back and fourth to see if the engine budges at all.
As a safety precaution you should unplug the MAF sensor (the big plug going into the side of the airbox) while doing the following. Unplugging this sensor cuts the power to the fuel pump so no fuel will be in the engine.
If you can get the engine to move ( pulleys will turn as the car rolls), then try the starter again ( no spark plugs). You may only get incremental movement at first, so repeat the above steps until the engine spins freely. Then reinstall the plugs, reconnect the MAF, and give it a try at starting. You will get a lot of smoke from the wd-40 at start up, but that will clear.
If the the wd-40 doesn't unbudge the engine, you can try pouring Automatic Transmission fluidinto the plug holes and letting it sit overnight or longer, and doing the same thing as above.