Write down the risky assumptions
List what must be true for the idea to work: the customer has the problem, cares enough to act, can be reached and will pay enough to support delivery.
Run the cheapest credible test
Interview target users, observe their current workaround, demonstrate a simple prototype or offer a manual version before building a full product.
Measure commitment, not compliments
Useful signals include a deposit, signed pilot, referral, repeat use or permission to follow up. Friendly praise is not demand.