Try To Fix Anything
Any true science fiction fan knows that the Butterfly Effect is some serious stuff. It basically means that even the smallest alteration you make in the past will ultimately affect the future in a very big way. So no fixing of the Liberty Bell. No fixing of past relationships. And no destruction of the first scripts for Star Wars Episodes I through III.

Find Your Parents
Sorry, McFly, but that would be a horrible idea. Not only do you risk potentially ruining any chance of your future existence, but you might see some things you don’t want to see…

Find Yourself
Rule #1 of time-traveling is never to find yourself. Although no one – to our knowledge – has ever traveled back in time and come face-to-face with their past or future self, most theoretical science assumes that you will undoubtedly explode (probably due to crossing frequencies or something.)

Visit Famous Disasters
One of my favorite b-movies is called Thrill Seekers, about a future where “tourists” can go back and visit famous disasters, escaping right before they would die. Cheesy? Yes. Epic? Heck yes. Enjoy the trailer below:

What I’ve gathered from the scores of times I’ve seen this film (no shame, no regrets) is that visiting famous disasters is probably the most stupid and risky thing you could ever do with a time-machine. Not to mention depressing.

Assassinate Anyone Other Than Hitler
Again, don’t change anything. It would be bad news bears for all of us. However,  when it comes to Hitler all bets are off. I know we’ve already discussed the Butterfly Effect and I’m well aware of the ramifications altering anything in the past could have for the future, but I’d be more than happy to take the blame for creating a world where Hitler was prevented from doing any of his heinous crimes.

Save Jesus
Think about it.

Redo Yesterday
There are two types of people in the world, those who like the movie Groundhog Day and those who have better sense. Not only does repeating your Yesterday sound completely repetitive, but it’s also impossible, seeing that you would run into the problem of mixing your past self with your future self. Plus, if you continuously visited Yesterday, you’d start creating multiple versions of yourself and over populate the world with duplicate yous. All readers with contrary opinions should consult my new favorite Wikipedia page on temporal paradox. And re-watch Groundhog Day.

Sneak A Peek At Tomorrow
Come on. Can’t you wait like 24 hours? That’s like wasting a wish on a new pack of gum.

Attend Your Funeral
Not only will you scare those in attendance, but who actually wants to know when, where, and how they die?

Witness The Last Day On Earth
Tempting? I think not. Again, who wants to know the when and where of something of that magnitude? Besides, I already know how the world ends:

Tell People About Your Time Machine
Are you crazy? Everyone would want to use it. What would happen if it got into the wrong hands? Anarchy! World war! Disappearing historical figures! Altered histories!

Conclusion
Don’t use your time machine. It’s too dangerous. You’d better just hide it. Or destroy it.