I threw one for my best friend today. It went REALLY well; she had no idea what was happening. Which is what you want when you throw these things. xD
I told her that we (my family and I) were going to the movies, and then swimming, so to bring her bathing suit. Everyone had already been invited and was going to show up at noon. So once everyone was there, I called her and told her to come over, and she showed up with her mom (who was in on it).
The surprise was a fun part. 8D She looked really confused, and then surprised.
Then we just hung out. Played DDR (my strange and wonderful friend Louis was playing with his butt. Don't ask) and Super Smash Brothers Brawl, and then we went to the pool.
Pretty fun day. :]