Here's what I think from the exposure I got with VCs (Please note I'm talking about VCs as opposed to FFF investors (Friends, Family, and Fools). Some of them may sound stupid, but for me they're facts. 
1- Being in a hyped industry. The hype now is about social networks (like this website) and entertainment. 
2- For first time entrepreneur, traction in terms of revenue is very important. The second best traction factor is the number of users of your system (if it's a system that can be used by anyone as opposed to a specialized system)
3- Rerfals made to the VCs about you through a mutual professional relation. Ex. You know the CEO of XYZ, inc. which was funded by a VC firm. That CEO is your key to that VC and, with some social engineering, to a higher valuation. 
4- Serial entrepreneurs can raise valuation based on previous experience.
A good website that gives cool advice to entrepreneurs raising money is www.venturehacks.com

Good luck