Ok. You’ve kept it short and simple. You’ve got a great product or service in mind and you want to see how well-received it’s going to be, so your first question is probably “Here’s my brilliant idea - would you buy it?” Stop right there. Don’t ask people the direct question unless you are sure respondents are ready for it. You may get discouraged by receiving negative feedback just because people don’t get it or don’t realize that your product/service/idea can help them.
Remember - you have spent long hours thinking about your creation but your survey respondents are just discovering it. Try to figure out their behaviors, or their usage of similar products/services. For instance, don’t ask “would you be interested in buying my product?”, but rather “do you currently use a similar product, how often, in which circumstances, and would you appreciate such-and-such improvements on it?”. Ease your way up to the big question.
Try to learn something about the respondents that will help you separate those who might be interested from those who aren't. Are they male/female? Do they already purchase something similar or would this be their first purchase in this category? Many research respondents hesitate to say they will definitely buy something that they have only just learned about – it's a little too fast. They are more comfortable honestly telling you whether they would or would not be interested in learning more about it. Understanding if you got their attention and WHY is often more useful than going for the killer question of “Will you buy it?”.