I hope you guys are working with recruiters to find out compensation ranges. I had a friend who once responded to a recruiter "hey, how about you come work for me". It's a lot easier to ask for more salary, stock, or benefits when you have inside information on what each company is willing to offer for each position!
We have a range of methods for gathering compensation range information. The more interesting question is: How can you actually execute on a good negotiation plan?
There is an enormous psychological component to this, and just knowing market rates and ranges for various companies is enormously important, but is only part of the problem (otherwise WealthFront and Glassdoor would have solved this problem already). Getting the right counteroffers and navigating the personal psychology here are enormously important too. That's where we differentiate ourselves with our expertise and guidance :-)