1) A good or at least interesting idea that isn't just mimicking what a dozen other companies are doing. 2) A founder with an impressive resume 3) Backers that know what they're doing. Elon Musk doesn't need to be on your board, but if you're money man is your dentist, you'll have to impress some other way.
I can't tell you how many pitches I get for "the newest startup in mobile advertising". There has to be something different about your startup otherwise you wouldn't be bothering right? (At least i hope so) You really need to identify that point of difference and highlight it in the first sentence. Most of us won't get much further unless you're really impressive in category 2 and 3.
Finally, a good pic of your founder/founders. Not a year book photo. Not a Zuck photo of some kid making faces in hoodie. A decent human shot of person that doesn't look like a canned shot. If someone choses to interview your startup that will be the first thing they ask for. Might as well make the process easier.