I would definitely go into the past. I'm a pessimist about that sort of thing, so I don't really believe the Earth has much of a shot with the human race involved. Plus, thinking about the future alone can give me anxiety attacks. So, yeah, definitely the past (I'd probably d something like what Lou did in Hot Tub Time Machine and use all the best ideas that are now present day hits) However, then I'd have to think about stopping 9/11-
[video=youtube;-TGj227OVKY]https://www.youtube.com/watch?v=-TGj227OVKY[/video]