<human>:  How do I plan a surprise birthday party for a friend?
<bot>: First, you will need to decide on a venue or location for the surprise party. You may want to consider the friend's favorite restaurant, a park, or even their own home. Next, you will need to gather supplies, such as decorations, food, drinks, and party favors. You could also plan activities, such as games or karaoke, depending on the type of party you want to have. Finally, you should make sure to invite enough guests, to keep the surprise a secret until the guest of honor arrives.