Over the years, I've seen a lot of innovation tools come and go. They get introduced with great fanfare at conferences. Perhaps a high-profile company or two starts touting the tool. Case studies get written up, and then comes the inevitable book.

More often than not that’s where it ends. The tool fades away. Nothing more is heard. But brainstorming is the exception.

Brainstorming is a tool with staying power. Invented by advertising executive Alex Osborn in the early 1940s, it is, arguably, more popular today than ever. Silicon Valley is all in. Startups start the day doing it. Walls and desk surfaces at Nike headquarters in Portland, Oregon feature whiteboards for brainstorming ideas.

Why has brainstorming enjoyed staying power, when so many other tools fade away? Perhaps because it works for generating ideas. Provided you do it right, and comply with some fairly simple rules. Over the years of leading ideation sessions for a wide range of clients, I've identified some guidelines to insure success.

Here are seven brainstorming techniques to keep in mind when you're planning your next ideation session:

1. Make sure the facilitator sets the right tone. Without a strong and enthusiastic leader, the session can easily veer off course. Participants may be reluctant to let loose and engage in a sense of playfulness. At the outset, the facilitator should stress the need for brevity in making comments, and simple things like one person speaking at a time, refraining from analyzing another person's idea, and the importance of building on other's ideas. The facilitators’ job is to build trust. When in this role, I walk around the teams of participants and observe the body language. I observe the way the team is approaching the assignment. If they've bogged down, I'll go into coaching mode, encouraging and even temporarily becoming part of the group to model the behavior that encourages risk-taking.

2. Use challenge questions to focus the session. While brainstorming is fun and mind-expanding, mostly we do it because we need fresh solutions to vexing problems. A fuzzy or unclear mission will produce fuzzy and unclear ideas. One way to clarify is with crisply defined challenge questions. My favorite is one I call "in what way?" In what way might we improve employee engagement? In what way might we add value to this customer segment? Such challenge questions spur the brain to search for alternative answers, and that's what creativity is all about.

3. Go for quantity, not quality. This technique is the bedrock of Osborne's tool. It is a means of discouraging judgement and analysis, aiming to surface the maximum number of raw ideas. Shoot for 100 raw ideas in 30 minutes, and set a time limit to keep the pressure on. The greater the number of ideas generated the higher the chance of producing a radical and unconventional solution. My informal research with ideation groups over the years suggests that it takes 80 to 100 raw ideas to find one that is worth further consideration.

4. Discourage judgment and analysis. The natural human tendency is to want to analyze and discuss the merits of ideas, but the objective of a brainstorming exercise is to dream up lots of ideas and withhold judgement during the process. The more experienced and educated the group (i.e. the more degrees you're working with) the more of a friendly drill sergeant you need to be as facilitator to get people out of their heads and into the flow. All criticism of ideas must be discouraged. It is the death knell to effective brainstorming. Instead, encourage participants to focus on turning their minds inside out for yet more ideas, for piggybacking on other's ideas, and for finding additional ideas after they feel "tapped out."

5. Encourage wild and even "absurd" ideas. To paraphrase Einstein, "If at first an idea doesn't sound absurd, then there's no hope for it." By encouraging participants to suspend judgment of ideas, participants will feel free to generate unusual ideas, bold ideas, humorous ideas and even absurd ideas. As facilitator, if you're not hearing frequent bursts of laughter and enthusiastic cheers now and then, somebody out there is playing the role of Debbie Downer. Find her and put a sock in her mouth! If your group is known to be overly-linear and prematurely analytical, plan a fun exercise to start the session that has nothing to do with the main brainstorm objective. Lately, for example, I've started sessions by doing an exercise where participants design better shopping carts, coach airline seats, or driverless cars, just to get folks thinking out of the box.

6. Make sure everyone's ideas get captured and displayed. This is essential. To ensure that introverts as well as extraverts feel their ideas have been received, all ideas must be captured and eventually displayed on some common medium. Sometimes I'll start a session by displaying the challenge question ("In what ways might we do X differently?") on an easel pad, and kick off the brainstorm by having participants jot down their ideas on individual sticky notes for a period of quiet time before coming together as a team to consolidate the ideas (eliminating duplicate ideas). The trick here is having a common medium to display ideas and everybody feels an equal contributor to the session, and no idea gets lost.

7. Use "dot-voting" to rank the ideas. After you've brainstormed and stormed yet again, you'll observe that participants are tapped out. At this point it's important to take a break before beginning the analysis and idea selection phase. One method I often use to energize the idea selection phase is the simple tool called dot-voting. It works like this: each participant is given five or more sticky dots (available at office supplies stores) and instructed to place their dots as votes on the ideas they believe have the most potential. Participants are free to vote all their dots on a single idea (if they believe it's particularly compelling) or to spread their dots to different ideas.

Once the voting is completed, you'll have a visual representation of the group's thinking. Rearrange the ideas so that the ones with the most dots are grouped together and ranked from most dots to least. Talk about the ideas that received the most votes and decide on next steps.

Leading these sessions is one of the most fascinating roles I am invited to lead, and I’m always learning. I’d love to hear from you as to what some of your favorite techniques are for getting groups to generate ideas. I invite you to share them with me, and perhaps I’ll write them up in a future Forbes blog post.