5 rules you should stick to if you want to form and keep a strong friendship with someone, if any of these things start to go missing, the friendship will weaken, like a brick being removed from a wall, and the more of these bricks that go missing, the weaker the friendship will become until it collapses all together...
1. Be Fun: no-one wants to be friends with a moody cow, so make sure you try and be happy and fun to be around for as much as possible. Learn how to entertain your friend and find things that you like doing together.
2. Honesty: It's ok to tell an occasional white lie where necessary, but generally, be as honest as you can, be yourself and don't try to be anyone you're not and most importantly NEVER LIE TO YOUR FRIEND!
3. Sympathy: Learn to know when your friend is feeling upset, what might upset them, and how to make them feel better when they do get upset. Being in touch with their feelings is key to making any friendship work.
4. Loyalty: If you ever hear any gossip going around about your friend, or if another person tells you something that they really ought to know, then tell them! This will ensure your friend that you are always looking out for him/her and will give them the impression that you are their knight in shining armour!
5. Trust: NEVER tell anyone else any of your friend's secrets, or gossip, behind your friend's back! If your friend doesn't trust you- the friendship WILL collapse
Read more: http://wiki.answers.com/Q/What_is_in_a_friendship_contract#ixzz1IQu0eAGj