For going through security, if you have a laptop, be prepared to take it out and put it in its own bin to go through the x-ray machine. If your shoes have metal shanks, you'll need to take them off and have them run through the machine, too. (I just always take mine off unless I'm wearing sandals.)
Flights typically begin boarding pretty early these days, so don't decide to go buy a snack if you are getting close to your departure time.
Don't lock your checked luggage unless you have the new type of lock that TSA can open. Your checked baggage will likely be opened and inspected (they'll leave a little card in your bag letting you know they opened it) and if it is locked, they'll cut the lock off.
If you check the top of this board, there's a thread about items that you can't carry on with you -- you might want to check it out.
This may seem silly, but check your ink pens. There are a lot of popular rollerball pens (like the Pilot, ironically enough) that leak profusely due to the difference in air pressure in the cabin during flight. Some rollerball pen makers have addressed this and their packages are now marked "airline safe" for this reason.
Also, since you are flying on Midwest Express, I do believe you can expect fresh-baked chocolate chip cookies.
