How to get great results from brainstorming?
Brainstorming that works creates quantity first and then quality of results.
To find great ideas you need lots and lots of good, great, mediocre, and bad ideas. A large number of ideas even if they aren’t all good in themselves, spawn many more ideas and amongst the many will surface some great ones. And while you are getting started with your lists of ideas it is not possible to tell which ones will be the stand outs.
When a particular technique for brainstorming is used too often by the same group it no longer has the ability to raise the energy level like it did in the beginning.
Whom to invite? Look for members who will see the subject from a different perspective.
As diverse a group as possible will result in the most number of different options. So diversity along every dimension you can think of will improve your results. Diversity of roles in the company (including a customer), age, number of years in the job, background, education level and discipline, race, sex, country of origin, language, and anything else you can think of whether or not it would seem to apply to the question at hand. And most of all, diversity of thinking styles based on any of the popular instruments or techniques (e..g., DISC, Mindex, Myers-Briggs, HBDI).
The definition of insanity: Doing things the same way but expecting a different result.
Different ways to get started
Start with a way to collect individual ideas before they are influenced by everyone else in the room.