You should have a proof metric - market traction, market proof, proof that they are not wasting their time on your site with half-baked ideas. You should also have some way to show that there has investigation and transparency into the crowdfunders. Try a group with vetting services like http://clearbusinessdirectory.com/vetting-services/ Lastly, you should have clear focused categories that are not overrun with misfits. Investors may want to focus only on a particular area of interest. Make that clear.