There are a few different ways to hold contests. You can have something where one person is disqualified each round until you have the winner or you can have one person win each round. You can also hold polls to vote for the winner or you can judge it yourself.
#1 If you are judging a contest you can not be entered in it.
#2 You must have an ending date for your contest and your poll if you start one to decide the winner. Otherwise if you don't people may start holding the poll open until they win.
#3 If your deadline or you see the deadline to someeones contest or poll going over send me a pm and I will close it for you.
#4 You must play for. You can vote for yourself but please if you do make sure you really do think it is the best.