Google offers a really great report on the Dimensions tab that shows you how your display ads perform depending on how many times a user has seen them.  We’ve talked about the report before (along with how great it is), but by taking an extra step you can be confident with wherever you end up capping your frequency.  There’s nothing better than using data to make your decisions.  (There are probably better things, like ice cream or Chopped, but you get the idea.)  I talked about this report at Hero Conf this year, and it was so much fun that I wanted to spread the love even further.