You need to help other participants challenge the received wisdom and support anyone who is feeling pressured to conform.
Don't forget that one of the most dangerous phrases in business is "We've always done things that way". So, if you're in a brainstorming or problem-solving meeting you should encourage freewheeling and creativity.
It might help to break the meeting into smaller groups - each of the sub-groups are likely to develop their own distinct ideas.
Also, beware of any individual dominating the discussion so that everyone else follows their lead - you could ask individuals or small groups to critique that person's proposals.