NASA is not lying to you about the Moon landings; the Apollo missions really did land on the lunar surface, and there is an abundance of proof out there for anyone interested in facts instead of fiction. While debunking Moon landing conspiracies could be a full-time job for those who know the facts, one can only marvel at the tenacity of conspiracy theorists in their endless quest to perpetuate the lie that NASA never landed on the Moon. Interestingly enough, the most significant piece of evidence to support NASA's claim isn't really evidence, per se; at least not in the physical sense so much as in good ol' everyday common sense.
The single greatest proof that NASA's Apollo Mission landed on the Moon just as they claimed lies in the simple, undeniable fact that if it had been a hoax, there is no shortage of people out there who are qualified to expose the lie. Not only qualified, but extremely motivated to do so if doing so were possible in the first place. Do not forget, NASA accomplished this feat during the height of the Space Race with the former Soviet Union, and nothing would have pleased the Communist State more than exposing President Nixon and the United States of America as frauds. They did not, simply because they could not. That in itself is pretty substantial evidence the Moon landing wasn't fake. But if you still need a little more convincing in the form of fact-based science, there's a wealth of that to go around as well.