How to create a FOTM in a few steps:
1. Look for a champion, for example Alistar
2. Do a practise game where you roflstomp your friends, than get powned by an enemy Alistar
3. Make screenshots which show the OPness of Alistar
4. Go to the forums, create a topic which says something like "Alistar is very viable when played right"
5. Login with another account, create another topic which says "OMG Alistar so OP nerf naow", with the screenshots mentioned earlier included
6. Everyone will now play Alistar, forum will have a few threads with QQ (also your friends can also create some posts about it)
7. Watch everyone QQ, and finally nerf of Alistar