Get in the habit of inviting team members to challenge your ideas. Encourage them to constructively (and positively) criticize your plans. Make it okay for people to disagree with you.
This lets people know you value their input, and ensures that implemented ideas will be well thought out. By giving your sales people permission to disagree encourages teamwork, which, in turn, helps motivate everyone on the team.
Do remember, however, when someone disagrees with you he/she should raise the issue with you in private, instead of blurting it out during a team meeting.