4. Pack smarter and don't check a bag
Now that practically every airline charges you for any bag you check, it's prime time to learn to pack lighter. Just make sure you follow the carry-on rules.
5. Make sure to un-check the insurance box when purchasing online
If you want to protect yourself against a forced last-minute cancellation and losing all the money you shelled out for a big vacation abroad, by all means protect yourself with third-party trip insurance, but not through your airline. If the only part of your trip you've prepaid for is airfare, it's generally not worth the insurance, especially if you're only traveling domestically.
6. Opt for airlines with the least punishing change or cancellation policies
If there's a good chance your trip dates may change, consider booking on Southwest. They are famous for their no-charge change or cancellation fees (they instead give you a credit for future travel). Similarly, Alaska Airlines will refund your flight if you cancel up to 60 days before your departure, and won't charge a change fee.