The Qick Guide to successful children's parties
The Quick version of The Complete Children's Party Survival Guide

Prizes

It is not necessary for every child to win a prize.
 
     
 
Keep the prizes small and simple. It is the idea of winning that appeals to children, not what the prize is.
     
Do not give out the prizes straight away. Show the prize and then explain that it will be added to the child's party bag for taking home.
 
     
 
If any children are concerned about not winning a prize, explain that everyone will be taking something home at the end of the party (i.e. a party bag).

For more detailed information on the above points see Chapter 6 of:
IntroInvitations