Five-year-olds know parties are very important and may enjoy the planning even more than the event itself.
That's why it's especially important to involve your five-year-old in the entire process. Theme parties work well.
Fives especially enjoy dramatic play, so have some props on hand for make-believe games (a pizza parlor, a fire station, a bakery, etc).
Fives are usually ready for games that teach right and left like Hokey-Pokey and Simon Says. While they're ready for organized games, some fives still have trouble taking turns, so plan accordingly.
Most fives have the small motor skills necessary to use scissors and string beads so they're now ready for crafts that involve more than simple finger painting.
Plan for a party of about two hours.