Don't under estimate the size of your airport. Some airports are huge (think Chicago O'Hare). If you're traveling on a tight schedule, make sure you scope out your next gate before you do things like eat or shop in the airport. Not understanding the dimensions of the airport can put you on a never-ending sprint to a gate you didn't realize was on the other side of the terminal.
Always check your flight times. You can end up waiting much longer than you intended for a delayed flight that a simple phone call to their airlines would have cured. Most people don't relish spending too much time in an airport lounge, so make sure you check your flight times and adjust accordingly.
If it smells bad, ask to be moved. You don't have to be tortured sitting next to someone whose body odor could make a pig faint, especially if there are open seats. While it might feel rude to ask your stewardess, you should think of your own comfort. Don't force yourself to sit next to Patty Over-Perfumed or Sam Too Much Old Spice either, especially if you're allergic.