S., the most important thing to remember is that little girls are clique-ish. Shoot for even numbers at the party. So, invite 3 or 5 or 7 girls. One less than your child's age is usually a good maximum. Before the party coach your daughter on the responsibility of hostessing.. making sure no one is left out, and everyone is treated with kindness... if she understands and accepts her role, then you will head off friction and tears.
Now, for the actual party... this was the most positively memorable party I ever had for either of my girls: my daughter and I premade chocolate, strawberry, and vanilla cupcakes and a double batch of 7-minute frosting. Then, we gathered supplies for individual pizzas and rootbeer (and/or coke) floats. Turn your kitchen table into a buffet of candy sprinkles and candy toppings. As the girls arrive they start decorating their cupcakes. Then, stack the cupcakes on a tiered cupcake stand with your daughters' on top boasting a candle.
Next, the girls make individual pizzas. While the pizzas bake, they are munching on a mini-fruit/salad bar.
After supper, its ShrinkyDinks time! shrinkyDinks is a special paper than you color with pencils and bake. When it bakes, it shrivles up and thickens. A quarter of a size 8x10 paper will shrik to roughly the size of a quarter or fifty-cent piece.. if you poke a hole in it before baking, it makes GREAT charms for necklace, bracelets, or zipper pulls... have each girl make one for the birthday girl, and one for herself. String them on ribbons with a jump ring and you have instant and indidual party favors. In addition, your daughter has a bracelet to remember her sleepover. I think my daughter still has hers... almost eleven years later... Shrinkydinks paper is found online, at Michaels, and Hobby Lobby
Next, exchange charms and have cupcakes.
After cupcakes, my girls played Twister and then went on a flashlight scavenger hunt in the backyard. Karoke is also fun, and/or a dance-off. just get them moving for an hour or so.
Ask around and borrow a foot spa for each pair of girls. Help them give each other pedicures and paint toenails.
The girl in the chair sips on her float while her partner pampers her... then they switch.
Set up sleeping bags in the living room and start the movie. They will likely fall asleep in the first 30min. :-) happy slumbering!