In a word, test. Testing is what you should be doing for everything, and that doesn't always mean BEFORE implementation. Some of the best feedback you can get

In a word, test. Testing is what you should be doing for everything, and that doesn't always mean BEFORE implementation. Some of the best feedback you can get is through implementing and THEN validating. If it works, keep it. If it fails, lose it. If you're worried about sinking time into an idea that you're not sure of, talk to people. Build out a single landing page with the core ideas on it and see if people bite. Test. Test. Test.