**** NEW RULE ****
I have been discussing this with friends here for a bit, but I do not understand why people where "3rd party jerseys" to any game. If I am at a Cubs v. Pirates game, do you think it is appropriate to wear a Brewers, Cardinals, or worse, a White Sox jersey to Wrigley? It is the dumbest phenomenon. I say go with a gray t-shirt, be Switzerland. If I were to go to a Blackhawks game, I do not sport my Penguins jersery nor do I don a Steelers jersey at Soldier Field. My ruling on this matter is this, if you want to wear a 3rd party jersey, save the money you spent on the ticket and drive to where your team is actually playing (home or away, I do not care) and show your support there.
On the same front, wearing a jersey from a different sport. I saw two guys wearing Bears jerseys, same city, different teams and sports idiots!
College caps are acceptable, you never know if they ALWAYS wear that hat!