Somewhere there is a team of United States Special Forces conducting recon. They have an elaborate plan, methodic to a flaw, discussed down to the most finite detail. While not making a sound, the team either walks through a jungle or drops over the skies of Grenada, perhaps Russia. The operational plan might include capturing a warlord or planning future invasions. And through all of the military precision, and the many people who know enough about the operation to pull off a successful mission, the world at large has no idea.
So if the details of a highly-covert, specialized military operation are so easy to contain, why can't people pull off a simple surprise party? The answer's easy. Unless there is the threat of a lawsuit, or a risk to national security, people love to talk. And when trying to keep something a surprise, the need to spill the details seems too tempting to stop. But there are ways.
Planning for a surprise party is the same as any other party. There is no need for panic. But when privileged information is involved, there is a tendency to go overboard in planning. Not to mention the nervous vibe that party planners give off with every breath they take. Thus, the same steps taken to contain the secret also end up killing the element of surprise.
So calm down and act naturally. Maintain military silence when it comes to party details. But don't treat the guest of honor differently, as if he or she is the leader of a communist country. After all, the goal is to have a fun time, not to seep into an enemy compound to release hostages. But the principles that the armed forces follow in planning and carrying out operations are the same principles that need to be applied when planning a surprise party.
Tell only those that need to know. Pick one meeting area to discuss details. Agree to only talk about the party at this particular location on the designated meeting dates. As ideas flow through the minds of the party planners, they should be written down and discussed appropriately at the proper time, no matter how tempting it is to pick up the phone and blab.
Plan everything that does not need a guest count. Then invite people. But be careful here. Don't exclude the people that should be at the party, however, use discretion. Swearing guests to silence doesn't always work. People break promises to talk. Minimize the advance notice of the party to no more than one to two weeks prior to the event. Don't worry about the short notice. The people who matter will be there.
Depending on the budget or the stakes of the party, purchase a pre-paid cell phone. This is the official phone of the party-planners. The RSVP's will come to this number. Vendors will call this number as well (caterers, etc.). Keep the phone off. Check it only when alone. Do not put anything in email. Again, remind invitees to keep quiet. Pay special attention to the potential guests known to gossip.
On the day of the party, keeping the guest of honor busy is more challenging than the NBA playoffs. Nobody can say with certainty what the best approach is with this dilemma. It comes down to particular interests. The best advice is to use the reason for the party as the reason for occupying the guest of honor's time. For example, if the party is in honor of a birthday, then occupy the person's time with a massage, shopping trip, etc., to allow enough time to decorate.
If the party details are leaked, don't lie to cover them up. It doesn't work. The only way to keep it a surprise is to convince the guest of honor that the party has been canceled. Solicit a few of the trustworthy invitees to help reinforce that the party has been called off. If there are gifts involved, have those invitees take their gifts to the guest of honor and express extreme regret over the demise of the festivities. Then keep planning.
But don't put important relationships in jeopardy. If the person of honor is a spouse, and he or she picks up on the secrecy, don't let the cover-up go on too long, especially if it is causing strife. Secrets can build tension. And in the end, no matter the good intentions, the party will be tainted by arguments and accusations. Confess the details and plan the party accordingly. And if forced to reveal the plan, remember, there is always a second chance to surprise somebody who is deeply cared for.