Brainstorming is one of the most well-known and frequently-used creativity techniques. Although the original brainstorming has several merits, it also has some drawbacks in its applications. Thus, lots of its variants have been introduced. Reverse Brainstorming, Cordon Method, Phillips 66, Brainwriting, 6-3-5 Brainwriting, Crawford Slip Writing, Nominal Group Technique, KJ Method are some examples. These techniques are classified into some categories, and their main characteristics are examined in this paper. Guidelines for applying the techniques are also provided.