Talk about the features of your product and ask questions directed around its use. For example, explain a feature then ask the respondent if they would be interested in that particular feature. Position the features as if you're solving a pain point for the user. Example: "If the product had the ability to synch all your leads to every device you own, saving you the process of manual entry..."
Likelihood of Use
This is where you want to be very direct--ask them if they will use the product based on how you presented it. Ask them questions about whether they would be more or less likely to use the product based on how it works. Never ask if they will buy it or how much they will pay--people buy based on emotion--you won't get accurate data. You simply want to know if they like the concept and if they would use the product if it was available to them.
Keep your survey short. There's no rule of thumb on questions but try to keep them to yes/no, multiple choice so they can be answered quickly and make sure respondents can finish the survey in 5 minutes or less. Always give them the ability to provide free-form feedback however if they decide they want to do that. Make it optional. I hope this helps.