There are a few things you can do, in addition to the classical workshop preparation, to ensure that you get better results in your workshops. Here are a few things I practice and that I find work well:
Homework for participants: Give people homework to do before a workshop. This can be either some information to read so that everyone is already properly briefed or a reflexion exercice with a question that people can try to answer and that you'll build on during the workshop.
Interview participants: For more complex workshops that can take several days or are on very emotional topics, I like to meet a few key workshop participants before the event to verify my assumptions. I usually ask: "What would be the dream result for you at the end of this session?". I also, from time to time, ask: "What do you usually hate about workshops?"
Obviously, these tips depend on how much preparation time you have and how much access you have to the workshop participants.