Doug Lea contributed the following checklist for writing great patterns.

A Pattern...

• Describes a single kind of problem.
• Describes the context in which the problem occurs.
• Describes the solution as a constructable
• Describes design steps or rules for constructing the solution.
• Describes the forces leading to the solution.
• Describes evidence that the solution optimally resolves forces.
• Describes details that are allowed to vary, and those that are not.
• Describes at least one actual instance of use.
• Describes evidence of generality across different instances.
• Describes or refers to variants and subpatterns.
• Describes or refers to other patterns that it relies upon.
• Describes or refers to other patterns that rely upon this pattern.
• Relates to other patterns with similar contexts, problems, or solutions.