Battery goes dead

About 2 weeks ago, i left the lights on the battery went dead. I had a fried jump start me, it worked fine. Then a couple days later the battery died when my son was driving it. We bought a new battery. It seemd like the car was doing fine. Then yesterday my battery was dead again. I did not leave the lights on this time. my friend jump start it. I drove it home, about 5 blocks, it wouldn't start again. My husband charged the battery the lights inside the car came on , but when he tried to start it it went dead. What could we check to see what the problem is? Thank you if you can help us out.