Surprise birthday parties are not just for children. Indeed, adults can benefit from knowing that the people around him or her cared enough to put in the kind of time and effort it takes to throw a decent surprise birthday party. However, throwing a surprise birthday party is no small gesture of love or gratitude; it is a full-blown event requiring lots of time, energy, planning, and probably more than one headache if it is going to be pulled out correctly. All the same, when you see the surprise and joy on the guest of honor's face, you will know that all the hard work had been worth it.
A good surprise birthday party requires that the guest of honor know absolutely nothing about the party. That means that everything, from the surprise birthday invitations to the party to the decorations must be done completely covertly. For a child, this is relatively easy. For an adult, this is very difficult. Because it is so difficult, it is important to have as much support as humanly possible. That is where the surprise birthday invitations come in. Surprise birthday invitations must be handled delicately. On one hand, people need to know far enough in advance to keep their schedule clear and come up with a really good fib to tell the guest of honor with regards to his or her whereabouts on the guest of honor's birthday. It would be wise to coordinate excuses, if everyone the guest of honor knows is all the sudden sick on the day of his birthday, he or she will know that something is in the works. You will probably want to coordinate excuses and the guests can start dropping hints that they will no be available on the day in question. For example, let's say the party is planned for June 10. One guest might casually mention to the birthday boy or girl that her in-laws are coming into town in "mid June" that way, when she declines to do anything with the guest of honor on his/her birthday, the excuse seems more plausible because the guest of honor already knew that might happen.
One of the cardinal rules of a surprise birthday party is that it takes place in the home of the guest of honor if at all possible. This is because it is easy to get a person to go home without arousing suspicion, but sort of difficult to get them to go anywhere else. What if, for example, you wanted to have the surprise birthday party at a restaurant but at the last minute the guest of honor, no knowing, obviously, about the surprise, wants to eat somewhere else? That is why it is best to have it at his or her house. You will also need a decoy, someone, to get him or her out of the house and back a few hours later on his or her big day so you can set everything up.
You are going to need everyone to help out with this. You can recruit people to bring food and drink and even the cake and decorations. Make sure everyone gets there in plenty of time to help set up so that there is nothing left to chance.
Lastly, think about having the surprise birthday party on a dear near, like a day or two before or after the guest of honor's birthday instead of on the birthday itself. People might suspect a surprise birthday party on their Birthday, but what about two days later or two days previous?