I’m rarely able to sleep on a flight, so I keep myself amused by bringing a couple different paperbacks (a fun easy-to-read book of fiction and an intellectually engaging non-fiction type book) small deck of cards (teach yourself several types of solitaire before-hand) and a small pad and pen for a journal. Sometimes I bring a small art pad and a drawing pencil and pen. Of course, you generally end up sketching the back of that guy’s head and somebody’s arm. But, if you’re creative, it can be fun.
I bring snacks (trailmix, dried fruit, sometimes a couple of buns or a hunk of sourdough). As others have mentioned, it’s a good idea to drink lots of fluids. I bring an empty water bottle and fill it up with water from the flight attendant. Then you don’t have to rely on catching their eye when you need a refill.
Your attitude is important. If you expect terrible treatment, it just makes things worse. For some reason, my luggage is usually searched, but despite that, I generally have positive interactions with security personnel. If they single you out to search you or your luggage, don’t panic! It happens to loads of people. Be polite and follow their instructions. Trust me, they want to finish and move on to the next person. So, make it easy for them to be efficient about it. Regarding flight attendants, I’ve always found them to be helpful and friendly. Sometimes it might be fake-friendly, but y’know, they do it all day long, in cramped conditions with crappy air.
Shoot, now I see this question was asked last month. Anyway, my answer is good for travel in general.