Having traveled a lot with both my children (boy now 7), here are my tips:

1. Book a window and aisle seat. When you check in, ask if they can block the seat in the middle (nobody really wants to sit with you anyway )
2. Bring lots of activities and bring them out one by one. Save some for the way home. I have an IPOD touch for my son loaded with his favorite movies and games. I bought special headphones that fit him properly (not the ones that come with it because they would fall out all the time)
3. I found that if the flight left really late at night that sometimes he would get past the point of being ready to sleep and would sometimes get crazy and hyper. Flights that leave around dinner time work better for us.
4. If you prepare for battle (understand that you will not get to read a book or watch a movie), then you will find that the flight is better than expected.
5. Always bring extra clothes for you and your son. You never know what will happen.


Good luck !
Tara
www.thetraveltot.com