Whew, Lots of questions at once, but I'll do my best...
I would like to use the pre check in on AA for STL. I am not sure how to do this? ...
Go to
www.aa.com. On the right side of the screen about 2 inches from the top, click on Flight Checkin, and follow the steps as given.
Do I print the boarding passes? Do I cut them out of the paper? Will they be accepted by TSA?
You can print them if you like. Bring the entire sheet of paper, don't cut it. Yes, TSA will accept a home-printed BP.
Do I check bags with the guy at the entrance?
You can if you like, as Horace pointed out there is now a charge for using the curbside checkin, and you should tip on top of that. (The Skycaps at Lambert are independent contractors who get their income from tips only, the airlines do not pay them.) Checking in at the counter won't cost you anything.
Can he get the wheel chair for Grandma?
He can't get it, but can order it, as can the agent at the airline counter, or a security guard if she doesn't ask for it until past security. An attendant who works for the airport will bring the chair to you where you are waiting, and will push the chair for you. NOTE that wheelchairs are NOT available before 6 am, and it can sometimes take up to 30 minutes to get the chair after asking for it, so factor in that time.
When does the bags and security open ? Our flight is early. Can we check in the night before? (we are staying by the airport)
You may check in online the night before, but if you are asking if you can check bags the night before, the answer is no. AA's counter at Lambert opens at 4:30 am. The Skycaps usually don't open up until a little past 5 am.
AA flies from the main terminal at Lambert, primarily from the C concourse. You should know that the security line for C is always the worst one in the airport; give yourself plenty of time. I haven't flown AA since 8/10, so I don't know if the B concourse security line is open at the moment, but if it is, use it. It is hard to find, so the lines are normally much shorter. The B and C concourses are linked just past security, so you can walk from B to C; it's about 50 yds. extra. Here's how to find it: If you come down the escalators headed toward the C gates' security and see a huge security line, turn to the left and follow the wall backward. Behind the escalator/elevator shafts, to your right there will be a nearly hidden security gate marked "Concourse B". It only has two lines, but very few people know it is there, so it very seldom has a crowd, though it is not always open.