I would go back in time, see what this site was like long ago and to stop the end to good music.
By saying autotune will ruin the music industry and good music.
So Justin Bieber will not be a celebrity.

I would go back to when my favorite classic rock bands were still around.

I see no use in going to the past, since that may merely alter the present. I'd go to the future and see what sort of advances had been made in medicine and science. If I had multiple trips, I could go to the past to see how the earth was formed, whether controversial historical accounts are true, and see whether the universe had a time of origin.

I would use it for my own gain, or even the gain of people that I like (Family and friends).
Like first off correct any mistakes that I made in my life, than go to the future to get stuff that haven't been invented in the future so I can make my life easier (Of course, assuming the future is a good future, with huge technological advances and not just some post-apocalyptic future.

Maybe become some sort of time travelling hero, saving people and solving problems around time!
Or take the more fun route and use my time travelling for evil and become supreme ruler of the entire space and time!

I would go to the future to see if like everything was electronic in the future. Like if we had hover cars and all that kind of stuff. I would also stalk myself to see what I would be like in the future.

Well scientists have a theory that if you get into a rocket/spaceship .Etc. and fly into the outer ring of a black hole but go in at just the right angle at just the right speed and at just the right time then you'd be able to fly around it without getting sucked in and then when you come out you'd be 1-3 years into the future (This applies for a super massive black hole only) (No I am not making these things up) So theoretically you could go into the future. Which would be cool to see if the world was destroyed by humans not taking care of it. However if we could go BACK in time then I'd like to go to WW2 so I could completely understand everything that happened. From the treaty of Versailles in 1918-1919 to the Munich putsch to Hitler's rise to power and then to Hitler's fall in 1945.

I would travel to the American pacific coast in the 1950's. I'd love to see how simple life was back in those days (or at least, how it was reportedly simple).

Two words:  lottery tickets.

Few people who win the lottery are emotionally prepared for it.  They squander the opportunity on high living and generally wind up worse than they are.  That being the case, they couldn't complain when I was right there sharing the money-or winning it a week beforehand when nobody had the winning numbers.  I don't want to try to correct the world's wrongs; I'm smart enough to know I don't understand all the impact of what I'm trying to do.  Stop Hitler and who knows what might happen?  We could be having religious war with the Jews right now, for much the same reason he gave-they control too much of the money flow, and we are in a bad fiscal situation.  Win Vietnam and the Rambo movies would never be made, not to mention that the people we were fighting for didn't honestly care (witness the way they were shooting artillery into the dirt to more easily return the casings for salvage money) and wouldn't have kept the Communist forces out anyway.  But I can at least get a nice fortune to do what I please with and without particularly harming anybody.

I would have to travel to the 1980's because that is when Nintendo first started making NES games, and having a few of those sealed in the box would be a few thousand dollars now.