The fastest way: Decide on your topic. Your offer. What you think your potential customer intimately wants to achieve.
Next, Set up your registration page and send traffic to it. If people sign up… there is your proof. If no one signs up, tweak the offer a bit more and try again. This way you are only out a couple days max.
I have setup presentations before where the signups were so low I just cancelled it, made it a little better, pushed the date out and did it again and it worked great.
You can do all the research in the world and nothing will give you more information than doing it and letting the people tell you if they want it or not. So remember not to spend to much time on this.
Just get it going and soon you will know if you have a winner or not right away.