Here are a couple tips I used when mine were little:
When you book your flight, if you get to pick your assigned seats, request a window and an aisle seat (not the middle). As the plane fills up, those single middle seats are the last to fill. If it's not full, you will get the whole row for the price of the 2 seats. If it does happen to fill up, you can always trade places with the person in the middle (trust me, they are not going to want to sit BETWEEN you! :) )
This is going to sound crazy, but my pediatrician is the one who suggested it. Right when you board the plane, give your little one a dose of Benadryl. Have a bottle ready (or nurse them) during take-off (and make sure they're hungry for it.) The swallowing will help with ear pressure, and as they drink and the Benadryl takes affect, they will fall asleep. This one always worked like a charm for me!
Finally, take a BIG diaper bag on with lots of easy snacks--Cheerios, etc. Keep their mouth busy eating, and they won't be crying. Also make sure to have their favorite cuddlies with you.
Just do your best to keep them happy, and if people are annoyed by your little one, that is THEIR problem. We were all little once...