Will turn over but wont fire.

My g/f 99 malibu just quit on me. I know about as much about cars as a 6 month old infant does so im somewhat car retarded when it comes to issues with them, so any help would be amazing. At first i thought i just ran out of gas because it was initially low on gas. So i filled it up with about $4 worth of gas. It turns over just fine but thats just that.. it turns over but wont start.. any suggestions anyone. Please and thank you.

possible fuel pump // have someone smak bottom of tank while u try to start it // it if starts /replace fuel pump /