I fly a fair bit and often get asked about airlines. My top tips:
1: Fly the airline with the most flights from your preferred home airport.
2: Join everyone's frequent flyer program.
3: Book early, at least 60 days before your travel dates. If you wait until the last couple of weeks, you will pay more and have fewer options.
4: Decide what seats you like, and always try to select your seats.
5: Get an airline credit card that gives you free checked bags. If you fly a couple of times a year, the checked bag fees will offset the annual fee. And most cards get you into an earlier boarding zone.
6: Check a bag! Don't try to carry it all on. Trying to find overhead space is a struggle, and if you are limited to one 20-inch bag, you are going to look like a homeless person before you get home. Check a bag!
7: Pee before you board.
8: Don't be afraid of connections, changing planes, but allow an hour at most airports. The barely legal 30 minute connection, will result in rushing and worrying about missing your flight.
9: When something goes wrong, don't blame it on or take it out on the airline staff. Being rude, won't get you anything that being nice won't get you. I stood in line one morning, listening to person after person rage at the counter agent about missed connections. When it was my turn I simply said, "I know if you could waive a magic wand you would, what can we do to get me home today?" I got the next flight and a seat in first class.