A lot of times, all it takes to keep a kid happy is making sure his/her basic needs are being met
... and also, may we suggest you (not
you, ONTPax, i know exactly what you're like and yourself and the wee one are always welcome in any of our flights), as pax traveling with a young child, don't feed the little one millions of chocolate bars and other foods containing sugar while waiting for the airplane; it'll only make the child happy for 2 minutes and unhappy for 2 hours. Entertain the child, show him/her the airplanes on the tarmac, have a walk through the terminal, have a read of a children book, whatever you do, DO NOT GIVE THE CHILD SUGAR!!!
Make sure you're prepared for a situation where you can't get the baby food warmed up in the a/c (boilers don't work, or whatever reason). Many airports have a "baby facility area" where you can warm up the food to keep you going for a couple of hours.
The little ones are ever so unpredictable, but ensure that the nappy is changed/child is asked if he/she needs the toilet before the flight. Chances are, not big but they are, that you might not be able to use the toilet on board during boarding; the a/c might be refueling therefore, for safety reasons, no one can use the toilets.
Instead of going to sleep as you "need a break" from the little one, make an effort and entertain the child during the flight. I see many parents using portable DVD players, or paper sheet and colored crayons - most of them are drawing airplanes and fluffy clouds and the pilots, which is ever so sweet; Of course that'll be a bit tricky to do with an infant (under 2yo), but i see mums and dads keeping the baby happy with making funny faces, or wander in the cabin (we don't mind you know, if you're blocked in the aisle between the 2 trolleys just ask us and we'll let you get pass).
We can tell bad parenting from good parenting. If a baby is crying and the mum looks like she doesn't give 2 *****, we don't like it but somehow we step in and try and help with the situation.
If the baby is crying and the mum looks either embarrassed or worried, we still try to help and sometimes we feel bad because we can't do anything to help out with the terrible ear ache (which are horrendous for the little ones) the baby might have.
In the end, it all comes down to parenting. Some are good at it, some are bad.
Life is not perfect, and nor am I.