This year my son wants a Harry Potter Birthday, and since the movie Chamber of Secrets will be out, makes it even more fun to do. First I printed out the invitations on the computer, I downloaded the howl holding an envelop and wrote the kids names on it, and it's carrying a note saying that they have been accepted to the Hogwarts school of magic. I've incorporated the 2 movies together for this party. So when they arrive at the house, they are greeted by 2 owls on the front steps,(plastic ones for the yards) and on my door I took some ceiling tiles and painted them to look like bricks and put them all around the door with a sign saying platform 9 3/4 and put grey streamers coming down,so the kids had to pass through them to enter the house. Once inside the kids are sorted out by putting a witch hat on and I put talk abouts in the hat and someone else at the other end sorting the kids, so it looks like the hat is actually talking. Once sorted I put a house sign around their neck that I printed out on the computer and place a cape on them too. ( I bough some fabric and made a simple cape) Then all the kids were invited to create their own hats, I have pre-made the hats, but left them blank and the kids decorate them with stars and markers ect... After we have potion class, I found some good ideas on the internet here are 2 (Pour milk in pan, allow to warm, place a few drops of different colored food coloring into the pan of milk, next, place a few drops of liquid soap, note: makes swirls.  Pour soft drink into glass, add some salt and then some powdered jell-o into the glass, watch jell-o bounce up and down) Then we have herbology class, just purchase small pot and let kids plant a seed they can then bring it home. After was the hunt for the Bassilik (snake) the kids walk around the yard and look for it, I have it on the clothe line, it's a pinata snake and the kids have to break it open with a broom stick that I have disguised as a sword. After the activities it's cake and gifts and the kids will settle down in front of the tv and watch Chamber of Secrets while waiting for their parents.  As for decorations, I have painted 4 big house banners and suspended it by satin ribbon in the kitchen and put glass jars with weird things in them and named them all. I also used a washable paint and painted my patio door to look like stained glass with all the houses crest, very nice effect. I also painted in old style the Banners, Great Hall and Forbidden forest, dungeon ( going to my basement) The feast consist of chocolate frogs, jelly beans, with a card that I have printed out with each jelly bean color and supposed flavor, like a red jelly bean is dragon's blood etc... Magik Cool-aid, Gummy worms and HP cake, I also bought the matching Chamber ass. at a local party store to complete the decorations. The kids will bring home a surprise bag, that includes HP bookmarks, witch I printed out from the HP website.