Come with a rough brief rather than a finished one. First, tell us who is in the room, or what the organization is trying to change. Next, share a date range, even if it is still soft. Then, if there is a budget band, say so early, since it saves everyone a round of guessing. Above all, describe what a good outcome would look like to you.
Speaking enquiries move faster once the media kit and technical rider have been reviewed, because most logistical questions are answered there. Consulting enquiries usually begin with a short call and no obligation. Ultimately, whichever route you take, a real person reads every message and replies.