Summarize this article in one sentence.
When your honoree arrives, you can jump out and yell surprise,  but you can also add to the surprise by making a lot of noise. Give your guests instruments like whistles or shakers, or instruct them to sing or clap when the honoree arrives. Instead of the traditional surprise approach, have guests walk in on the guest of honor, instead of the guest of honor walking into the surprise. Choose a day that appears "typical" to the guest of honor, and instruct your guests to casually file in one by one. Watch your honoree glow with shock as they see the number of their loved ones arriving to honor them. If you are planning an outdoor event, surprise the honoree by showering them with items like silly string, or water from water guns or water balloons. If you are choosing the water option, make sure the party is water-themed so that the guest will dress appropriately; either have on a swimsuit or have a change of clothes handy. Consider your honoree's reaction before taking this route. Some people will not be happy about getting their clothes wet or having their hair covered with silly string. Begin serving food and drinks ahead of time. This will help detract from some of the spotlight and ease the honoree into the party more easily.

Summary:
Make as much noise as possible. Consider a quiet surprise. Use silly string or water guns. Make sure your party is in progress, when the guest of honor arrives.