To try not to think about someone brings to mind the old story of a medicine that only works if you don't think about monkeys. Of course, once you tell a person that, the one thing they will think of is monkeys. The same applies to any one advising you "just forget them." It's just not that easy. First, find some other activity to keep you busy. It doesn't work right away - especially if you've started the activity with the express purpose of forgetting that person. It does shorten the period, however. Beyond that, only time works. One other piece of advice. It this is a romantic relationship, be very careful about starting another one. In the U.S., it's called "being on the rebound". It is not suggested try to form another relationship very soon after breaking up. I am also assuming you didn't get a tattoo of the person's name anywhere on your body. In that case, forgetting them becomes much, much more difficult - at least in my experience.

Don't go to any of the places where you know that they will be.

I think the best way is to get a passion for something : drawing, reading, music... An activity which can make you think about something else :)

Get someone else... ^_^

A long time ago I started to learn Chinese for that purpose; years passed by, now I forgot almost all my Chinese, and still think about that dear someone. Is this answer of any help ?