Some off of the top of my head.
Go to
www.flyertalk.com and join the discussions there. It is a huge network of frequent fliers and will answer any question you may have.
www.seatguru.com will help you find a comfortable seat on most carriers.
Concentrate on one airline or alliance (skyteam, star alliance, etc.) and gain elite status - travel is much more fun when you are sitting in first class for free.
Join the airline's lounge. It makes hanging out in airports all day much more comfortable, the agents there can take care of issues without a long line, and the snacks/drinks/newspapers (sometimes internet) are free.
Get a good pair of noise canceling headphones - makes flying much less stressful without having to hear the drone of engines for nine hours. (See the travel technology forum at Flyertalk for recommendations).
Expect delays. Go a day early if it is REALLY important.
Travel light and avoid checking bags - makes rerouts much easier when necessary.
Know a backup plan if your flight is cancelled. Look at other routings, airlines, etc. The airline may not always give you the best option first. Carry flight schedules (I keep PDFs on my laptop) to rework your own routing. Most airlines will put you on a competitor if necessary, but this is usually not their preference since they lose revenue.
Keep reservations numbers for airlines, hotels and rental cars in your cell phone. Don't stand in lines when things go wrong - call. You will get taken care of much faster. Being elite with the airline should let jump ahead of other callers since they have special 800 numbers for elites. I got stuck in Amsterdam in March connecting to Munich (snow closed the Munich airport). Within 10 minutes of the flight being cancelled, I had a new seat the next day and a room at the Schiphol Sheraton for the night with two cell phone calls. I knew the flight was cancelled before it showed in NWA's system and the reservation agent back in the US took my word that it really was cancelled. Within an hour I was taking a nap in my room while many others were still standing in line trying to rebook. Since I did not have an urgent meeting that day, I was able to wait a day for the weather situation at my destination to clear up instead of having to hang around the airport on standby all day.
Make sure your cell phone works in the country you are going to, and international roaming is enabeled. Expensive, but worth it when things go wrong.
Inform your credit card companies where you are traveling. I almost had my Visa suspended because charges in Europe tripped their fraud monitoring. Carry a backup card just in case.
Drink lots of water on long flights. I will carry a bottle as I hate the taste of airplane water. (If the bottled water they are serving has a label, it is actually bottled water. If they took the label off, they refilled it from the galley tap.) I also remove my contact lenses or make sure I have plenty of saline solution handy as the dry cabin air irritates my eyes. Nasal saline spray is also helpful for longer flights.
Get used to your non-business traveler friends thinking how great it is that you get to have so much fun on business trips.