• Throw a silver-themed party.Andrew Bret Wallis/Brand X Pictures/Getty Images
  
  A 25th wedding anniversary is a big event. If you know a couple who are about to celebrate this milestone in their marriage, let them know how celebrated their love is by throwing them a surprise party.
  
  

Theme

• The first step in planning a successful surprise party is choosing a theme. Sure, you can simply pick up some paper plates and get a cake, but to make it really special and memorable, select a theme that interests the couple or correlates with the anniversary. You have several options.
  
  Because this is their silver anniversary, a silver-themed party is fitting. Decorate with silver elements. Cover tables with silver cloths. Fill silver balloons with helium and float them in the room so that they cover the ceiling. Tie silver ribbon around the backs of your chairs.
  
  Take the couple on a walk down memory lane by recreating their wedding. Bring in linens, balloons and other decorative elements that are the same color as those used in their wedding. Create centerpieces that feature their wedding flowers. You can even have a replica of their wedding cake made.
  
  Throw a party that is based on the location they visited on their honeymoon. For example, if they visited Italy, blow up pictures of the Coliseum and the Leaning Tower of Pisa and display them around the area. Serve Italian food.
  
  

Location

• After you've chosen a theme, decide where you are going to have the affair. For a more intimate feel, host the party at your house. You won't have to pay a rental fee and you won't be limited to any specific time frame.
  
  But if your home isn't big enough, or you would prefer a more formal affair, consider having the party at a restaurant. Although it will probably cost more, you won't have to prepare the food or clean up.
  
  

Revealing the Surprise

• Of course, you'll need to keep the party a surprise, and you will have to figure out how to reveal the surprise to the guests of honor when the time comes. When sending out invitations, let the guests know that it is a surprise. Also, ask them to arrive at least a half hour before the anniversary couple and to park their cars out of view.
  
  On the day of the affair, keep your poker face on. Ask the celebrants to come over for coffee or a celebratory bottle of wine if the party is in your home. Make sure the curtains are closed so the couple doesn't spot the guests as they walk toward your house. As soon as they enter the door, have your guests cheer them. Unfortunately, if your party is at a restaurant, the couple may spot you and your guests as soon as they enter. If that's the case, have the hostess walk them to your tables and greet the couple with warm hugs and good cheer.