A cipher is a simple method of modifying messages to make them unreadable, but still possible to recover. Common ciphers are Caesar, Vigenere, Atbash, and several types of substitution cipher. Other ciphers include polynomial ciphers such as Playfair, Foursquare, etc.
What is a cipher?
A cipher is an encoded message, usually by substituting letters for other letters, numbers, or symbols.
What makes a good cipher puzzle?
A cipher puzzle has to be solvable. There should be an intuitive and enjoyable solution path, and preferably one or more 'aha' moments. In case of multilayer ciphers, it's a good idea to provide the solver some confirmation after each step. See Code Puzzles: What (Not) To Do? for more on this.
How should I try to solve a cipher puzzle?
Try to see what kind of cipher it is - whether you need to use rot13, or Morse code, or unscramble something. Then, if it has more than one layer of encoding, you can continue with the same for the next level.
How should I answer the question once I have the solution to the cipher?
Make sure your solution fully fits the original message.
Answer the cipher fully, and provide a detailed explanation. Provide a line-by-line analysis if necessary to justify your solution.
Spoilertag content that directly relates to the answer, but do not write an answer entirely in a spoiler. Spoilertags hide part of a post by placing
>!at the beginning of a line.
See this Guide to Codes and Ciphers for more info.