Do you not want to be clingy, use these tips to help find out if you are, and how to stop!

[edit] Steps

Evaluate How much time do you spend with them? Sometimes people want to be alone and that can't happen with you near them all the time. Two friends are not supposed to spend all day everyday together! Let them spend time with there family and other friends.
Ask If you are worried about being clingy then just ask your friends and family! Let them know that they can be honest, and if you are truly worried about being clingy it won't hurt much if they agree!
Allow Let them hang out with other friends as well! You may get a little jealous, but it is better for you. It will give you some time to find new friends as well!
Never Do not phone constantly to see if they are busy or not. Just phone once, if they are not there then leave a message.

[edit] Tips

If they say you are to clingy, don't worry about it! Just shrug it off and accept it. This is what you were looking for anyway.
Get lots of friends, that way you will not only spend time with one of them. Thus, giving all of them some space.