Bjscheel is right, the day before checkout you'll get papers delivered to your room with a number to call about paying the baggage fees and then the morning of you can take your bags to the front desk for weighing in.
We got back Saturday and a few words of advice regarding Airtran... First, if you purchased new luggage I would not recommend taking it - find something old you don't mind being destroyed. I used to travel much more frequently and for over 25 years never had a major problem with bags until my last 2 airtran flights. Since then, one bag on each trip has literally been destroyed. Handles ripped off, huge oil stains on them, large gashes in the side of the luggage (it was soft luggage, so the gashes went through to the interior), broken wheels, etc. Airtran employees seemed to not care about this, either. In fact, after one flight one bag had to be tossed.
Also, if you are traveling with others and you did not pay extra to select your seats they will deliberately separate your party. The gate attendants will, if available, reassign your seats together but you have to specifically ask for this at the time of check-in. In fact, during both our departing and returning flights the gate attendants were helpful and both times acknowledged that the seat either next to me or my wife was available and then moved us so we could sit together.
While it may sound like I'm deliberately bashing the airline, I'm really not. Just calling it like it is.