First, make sure you've tactically stowed your liquids somewhere that is easy to get to without having to open up your entire suitcase in front of a massive queue of people who start to judge you for the abundance of Double Deckers you have in you bag. The chocolate bar that is not the public transport. Also, be careful about the bag you put them in. Usually I just use the same old one but recently it split thrusting my makeup to the four corners of Liverpool John Lennon. The security guy was less than sympathetic telling me he would have to bin all of it, even though I had actually brought a bag to put it in. Tears streaming down my face, he eventually handed me a brand spanking new bag that he just happened to have in his pocket. So in summary, turn on the waterworks if it looks like you aren't going to get your way.
Next, you have to do a recce of all of the available food outlets. This is of course only applicable if you haven't already brought some snacks with you. I must admit the only thing that made traveling on Boxing Day bearable was the feast my Mum packed for me, complete with sandwiches, Christmas Cake and whatever else I could carry! Eating helps to stop you from being bored. An even better solution to boredom is a good book (hopefully something quite weird) and a tube of Pringles next to you so that you can do both at once.
Talking of books, you need something engaging enough so that if you happen to have forgotten your headphones or your iPod has lost charge that you can block out the screaming children around you. (On a side note, there really should be quiet sections on planes like there are on trains.) I tend to try not to take anything too 'worthy' with me when I'm travelling. The in-flight magazine will always look more relaxing an option than sitting down to read In Search Of Lost Time. Agatha Christie works well; although not Death in the Clouds as you don't need that kind of imagery. Equally something funny and inappropriate so you can chuckle away to yourself works wonders.
If all of this fails then a cheeky mini-bottle of wine or a G&T on the plane along with a suitably glam eye-mask to block out the nutter sitting next to you works wonders.