I highly recommend that when you run an ideation workshop one person is designated as the facilitator. What does this mean?
A facilitator is someone who engages in facilitation—any activity that makes a social process easy or easier. — Wikipedia
The facilitator is basically the person who will lead the workshop. As the workshop leader I often recommend that this person isn't also generating ideas. Especially if there is a voting and prioritization exercice in the workshop. You can't be player and judge at the same time.
But what does the facilitator do? Here the key tasks of a facilitator:
Introduce the exercice: explain what the process is and explain every ideation exercice
Keep the timing: nobody likes to respect a timer, the facilitator serves as a social pressure to have a healthy time contraint that helps stay creative
Coach: help the people who are lost during exercices
Adapt: feel the participants and the process and know when the plan needs to be changed to arrive to the defined goal
Basics of Ideation for Innovation (Alpha version)
A future course teaching ideation theory and methods.