These things have worked for me:

-Snap a rubber band on your wrist (not too hard).
-"Cut" with red pen or marker (test it on your finger or something first to make sure it will wash off!).
-The Butterfly Project (google it! It's pretty cool).
-Draw or write stuff, such as quotes, where you want to cut.
-Watch funny YouTube videos.
-Count how many hours/days/weeks/months it has been since the last time you cut. Remind yourself how much you want to make it to the next milestone!
-Have a goal, like, if I make it until June 1st without cutting then I'll celebrate by going out to eat. Then set a new goal!

I hope these help. Good luck!