Well write out invitations to all the people you want to come to your party.
Then think of some games to play like truth Or dare would be fun or spin the bottle
Or if you have a games console thing like a playstation have a competition of girls against the boys...
then maybe watch a scary or funny movie with popcorn and coke/lemonade nearer to the end of your party
And for fun you could have a big gigantic piece of card for all your friends to sign and leave birthday messages for you and you can keep that forever! Have fun and happy birthday for the day! :0)