I'm not sure if you are talking about 'your' doubts or other peoples doubts. The reason I ask for clarification is your comment about being a non-technical co-founder and shopping your ideas made me think you were dealing with other people's doubts.<p>Either way, I think the answer is somewhat the same, and as a technical founder, I often have to get over my own doubts as to markets, capabilities, etc. etc.<p>First, understand that you will be hit with stages of doubt from others and from yourself. Nothing is guaranteed, for every twitter, there are 10 blippys. You don't have a crystal ball, and neither do angels, vcs, friends or anybody else. That's the nature of the game, if you aren't comfortable with that, you can't play.<p>I once created an online scheduling solution for businesses. Everybody told me it was such a great idea, such a great business. It fell flat on it's face, and fast.<p>I also built a concert search engine, and my brother (a successful start-up founder) looked at it and thought it was useless and sucked (he told me to focus on the scheduling stuff). the concert search got quite a bit of press and was fairly popular for a while.<p>So that's the first part. Understand and appreciate that you don't know, and nobody else does either. Start with your eyes open.<p>If you are looking at market doubts, consider how many companies were first thought of as useless or flash in the pan, which became something. HP wasn't interested in Steve Woznaik's computer (which went on to become apple), why would anybody want a horseless carriage, etc. etc.<p>On the flip side, play devils advocate with yourself and make sure you know why you are doing what you're doing. If you only half believe in it, you aren't going to get very far. You really do need to be all in and passionate about your product, but I'd say it is more important to be passionate about the market you are targetting.<p>If the doubts are concerning what you are offering, you need to consider that very carefully. You didn't specify what your background is, but you can't be just an 'idea' guy. What are you bringing to the table. Often technical people (myself included) don't feel that much of the business process/sales etc. is as important as the creation of the product (development), so you may have to work hard to ensure technical people understand what you are bringing to the table, and that they don't doubt your commitment and abilities.<p>A big part of getting over doubts is in how you're selling. Take a good look at Simon Sinek's Ted talk to help you sell your vision. <a href="http://www.ted.com/talks/simon_sinek_how_great_leaders_inspire_action.html" rel="nofollow">http://www.ted.com/talks/simon_sinek_how_great_leaders_inspi...</a>