Codes

• A spy uses coded messages to communicate with other spies to avoid giving away any information if the message is intercepted. There are several different types of codes. Substitution codes replace each letter with a different letter or number. Other codes rearrange the words or letters in prearranged ways. In a cipher code, symbols known only to the sender and receiver replace letters, words or phrases. Some spies use invisible ink to hide their messages on seemingly blank paper; you can make a basic disappearing ink by writing your message with a cotton swab dipped in lemon juice. Gently heating the paper will make the message appear.
  
  

Disguises

• The best disguises are the ones that don't look like disguises; successful spies try to look as inconspicuous as possible. Try changing the way you walk, adding a small limp or taking smaller steps. Carry a cap or soft hat in a pocket so you can cover your hair in an instant, and have sunglasses with you to hide your eyes in the daytime. Wear a reversible jacket; you can turn it inside-out and be wearing a different color. Experiment with different ways of wearing your hair.
  
  

Signals

• If a spy is working with other spies, they must sometimes leave each other signals that can't be interpreted by their enemies. Plan ahead so everyone in your gang knows your signals, and choose signs that won't draw the attention of anyone who happens to see them. For example, placing the garbage can on the left side of the driveway instead of the right could mean "let's meet," or wearing your backpack on one shoulder instead of both might signal "you're being watched."
  
  

Gadgets

• Real spies use high-tech equipment, but they are also skilled at using what they have on hand. There are many recipes online for homemade disappearing ink and fingerprint kits, and you can make a useful device for looking around corners out of a piece of cardboard, some tape and a couple of hand mirrors.