Traction. Traction of course differs from business to business, but the result from an investors perspective is the same... reduced risk. If you have a b2b saas its customers, preferrably paying. If you have a consumer mobile app its users and engagement, and so on.

DO go to meetings with a clear picture of your traction, metrics, etc. be able to explain and support that data.

DO NOT be wishy washy about your metrics, either know it or wrie it down. Investors respect the cheat sheet.

Finally, don't kid yourself with exaggerated metrics and tracking. Read this from Andre Chen if you arent sure - http://www.slideshare.net/andrew_null/zero-to-traction