Buy the cheapest ticket you can find for a sporting event (or other event) that you want to attend. 1 hour before it starts, log into http://10ws.co/1FtT8PU to see which nice (but not heavily secured) seats are still available at a price point higher than the competition (i.e. overpriced).
Write a few of them down and chances are you can sit there all game without any issue as the overpriced tickets won’t have sold so will remain empty.
If you do get told you’re in the wrong seat then just go to another set of seats on your list, failing that just go back to your original paid for seats.
Obviously this will work with 1 or 2 seats together but it rarely will work for anymore so it will depend on who you’re going with.
Thanks to El_Apostrophe on reddit