Turn the key to the "on" position without trying to start it, you should hear the fuel pump run for a few seconds then stop. Also you could pick up a cheap fuel pressure tester at an auto parts store and attach it to the valve on your fuel rail to get a true reading.
Do you have a multimeter? Check the battery to make sure it is reading at least 12V DC, the value should go up to about 13-14V once the engine is started, that lets you know the alternator is charging up the battery correctly.
When you say you "tap on the starter" are you crawling under the car and hitting the starter motor/solenoid? If you are and it works, it a good sign that the starter solenoid and/or starter is bad and sticking.