For my daughter's 13th birthday party, she chose a Harry Potter theme. I'm glad she decided far in advance! We were lucky enough to find Hogwart's stationary at a bookstore to print the invitations on. Each guest was told they were being selected to enter the school of wizardry, and to report to the train station on the specified date. We decided to decorate the backyard to look like Diagon Alley. First, our guests entered through the brick wall to get to platform 9 3/4. I had 3 huge sheets of cardboard tied to the fence and gate.  Each piece was stamped with a sponge dipped in red paint to make it look like a brick wall.  One side was Platform 10, one was Platform 9 and the middle was on the gate, the entrance to Platform 9 3/4.  As they walked in through the gate, the first thing they saw was a cardboard cutout of the front of the Hogwart's Express train, under the Platform 9 3/4 sign, all attached to the garage. We made up signs for: Quality Quidditch Supplies (attached to the shed, where we hid the prizes). Florrish and Blott's Bookstore (we brought out old bookcases from the garage, lined them with old books, magazines and my daughter's stuffed owls). The Leaky Cauldron (attached to the bar, where we had sodas for the kids). Gringott's Bank - Public restrooms available - deposits only (attached to the back door, leading the way to the bathrooms.) Zonko's Joke Shop (on the garage door, hiding more prizes for the kids) Ollivander's - Maker's of Fine Wands (over a table with the munchies for the kids) At Ollivander's, we had nachos (a favorite at our parties for years) and each child made their own magic wand. Pretzel rods dipped in melted chocolate, and then dipped into sprinkles or crushed peanuts). From my daughter's upstairs bedroom window, we tied fishing line leading down to the deck. We then attached a stuffed owl to the line.  I have a "memory button", that records sayings and sounds.  We recorded our messages to the guests, wrapped them in red napkins, tied them to the owl and "flew" the owl down to the guests.  Our very own homemade "howlers"! The highlight of the party was the scavenger hunt.  Each team was given a clue that led them to the next step in the hunt.  1st: they had to find the key to let Harry out of his cupboard under the stairs (we tied old skeleton keys under the deck). 2nd: they had to shop Florrish and Blott's for their school supplies (the bookcases were filled with books, magazines, quills, feathers, spiders, gold coins, pencils...) 3rd: find the dragon's egg with the next clue. (we made a nest of sticks and twigs, filled it with plastic eggs, raw eggs, hard boiled eggs, and blobs of whipped cream) 4th: find the owlery (we hung stuffed owls with message scrolls off of the bushes in front of the house) 5th: search the Magic Potions classroom (we put out bowls of jello, marshmallows, half cooked pasta and they had to fish around to find the clues) 6th: save your friend from the lake (we had plastic army guys thrown in the pool and they had to jump in and save them. We also had a "Catch the Golden Snitch" game.  We spray painted raw eggs with gold paint and had an egg toss.  We had so much fun watching the kids, I was glad we had extra eggs so the adults went a round or two!! The adults never laughed so hard and these kids running around!! We are still getting compliments on our ideas. My daughter is still ever so grateful for her party's success!! Hope you get some great ideas!