1. Park with your car nose out.
In the rush to catch the parking lot bus, it's easy to leave an interior light on; I'd guess that more travelers I know have had dead batteries at an airport than in any other situation.
If you return to your car to find a dead battery, broken windows due to thievery or any other potential problem, you'll want your car to be parked nose out for easier access to the battery, or for an easier hook-up to a tow truck.
2. Leave time to get to economy lots.
As airports expand, they need more parking spaces; those spaces are ever more frequently found in parking lots that are off-airport in every respect but name.
You'll also find that these lots are often significantly lower-priced than other lots. As a result, they're the best place for economy-minded travelers, especially for longer trips where you're racking up several days' worth of parking fees. Also, these are the last lots to fill up; if you're flying during peak travel periods, you may have no choice but to use these distant lots.
I've found that buses and monorails run regularly to these lots, but I invariably need up to 20 to 30 minutes more than I might in less remote parking lots. If you're looking to save money, or are traveling over a major holiday weekend, leave extra time to get from the lot to the terminal.
3. Pack essentials in your carry-on.
Recent stats indicate that, on average, at least one bag on every flight is lost or delayed. If there's anything you can't live without, pack it in your carry-on. This is especially true of items that are not easily or inexpensively replaced, such as running shoes or a lightweight raincoat.
“Traveling – it leaves you speechless, then turns you into a storyteller.” – Ibn Battuta
And you'll get through airport security faster if you pack your carry-on more efficiently. For example, have your quart-size plastic bag with liquids and gels packed in an outside pouch or right near the top of your bag so that you can easily pull it out for screening. See Packing Tips and What Not to Pack for more ideas.
4. Know your hotel information.
If a) your baggage is lost or delayed; b) you miss your connection and will be late checking in; or c) you are going to a destination you've never visited before, you'll want to have complete contact information for your hotel on your person. Before you leave home, print out the hotel's name, address and phone number, and program the latter into your cell phone. It's also a good idea to print out a map of the hotel's neighborhood, whether for your own use or to show to a confused cab driver.
5. Take old currency with you.
Exchanging foreign currency after you've returned home is a hassle, especially since almost no one spends any time in an actual bank these days. Why else do so many travelers have so much funny money lying around?
If you travel abroad with any frequency, and have any stray foreign currency laying around, take it with you the next time you cross international borders. Then, when you get some local currency, you can exchange the money from any other country at the same time.
6. Save your boarding pass.
Do you usually toss your boarding pass as soon as you step off the plane? You might want to reconsider. Your boarding pass can serve as proof of travel if your airline fails to give you the proper credit for frequent flier miles; this type of problem is particularly common if you're flying on a codeshare partner of the airline in question. Your boarding pass can also be useful as a receipt for tax purposes, particularly if you're self-employed.
7. Know when to use -- and when to skip -- the skycaps.
Skycap upside: You check-in at the curb, lose the bulky luggage and head straight to your gate.
Skycap downside: They don't give you a seat assignment, and they cost a few bucks. (Don't forget to tip; skycaps often aren't paid a full wage and depend on tips to make their living.)