Brainstorming is a the second step in a creative process after studying the brief and understanding the requirements. It's essential to immerse yourself in the subject. Learn about the business and the client as much as possible. Watch related material and talk to people about the subject. It's essential not to go to a brainstorming without a clear idea of what the job is about and without having a large pool of references in the back of your mind.
During brainstorming you are supposed to write down everything that comes to your mind without any consideration wether the ideas make sense or not. The objective is dump your brain and create a large pool of thoughts that later can be sifted through rationally.
Brainstorming can be done alone but it's usually more effective if done in groups.
Brainstormings should be informal and fun, but there are rules and techniques that ensure a successful idea generation process and they must be announced in advance.
It's best to choose a person informally leading the brainstorming. His job is to keep participants to the rules and help the ideas keep flowing when the group is stuck.
First rule is not to criticize each other's ideas as criticism shuts down creativity and automatically switches on the rational part of the brain which makes generating ideas much harder. When you hear a completely outrageous idea you know you're on the right path. Try not to reject such weird notions as idiotic. Build on them or simply say whatever they remind you of. Try to bounce ideas between each other. This creates an atmosphere of cooperative brainstorming instead of a competition between participants.
Make sure to allow everyone to participate, especially those who are shy at first. Don't try to say too many things at once. Let ideas linger for a little, so that other have time to think of something else based on your ideas. Introduce new thoughts when you are about have an uncomfortable silence in the room.
Try to brainstorm in a room without any decoration or distractions. Your brain will try to fill the void and this will help with the flow of ideas. You can also bring a box of strange objects made from various materials, colors, shapes and textures. Bring out the box only when the brainstorming starts to die down.
You can use many other techniques to generate ideas. Here are a couple, but you can think of new ones too. The key is to create a new context for the same problem.
You can switch between 5 minutes of solitary and 15 minutes of group brainstorming a few times. In the first 5 minutes all participants must write down at least one idea. And then in the 15 minutes everybody should present the ideas and allow others to react to it.
Another effective process is to write down 100 random words on small pieces of paper and put them in a jar. Then each person should draw one piece and use that word to generate an idea.
Use different body positions to change your perspective. Lie down on the floor, put a blanket over your heads, etc. These new experiences will reinvigorate your neurons.
It's important to do these exercises informally, it should not be like a Yoga class with strict rules. Allow the participants break the rules occasionally.
Traditionally the ideas are recorded on a board, but in my experience you will have better results if the ideas are not visible to all participants at all times, so you can avoid bringing them back to the same thought patterns when looking at the board. You can use the board to sketch out things that are part of the thinking process rather.
Finally, there is a tendency of groups to deviate from the subject. Remind the participants humorously to go back to the task at hand. A brainstorming should not take more than 30 minutes. It's better to do 3-4 sessions in different settings than one long 2 hour session.
Image from Modern Toss