It kinda depends on where that company is in its funding lifecycle. Startups usually have a recruiting stage right after the series A round is complete, so there's a bunch of articles and blog posts about that situation. Here's a short reading list: http://michaelochurch.wordpress.com/2012/07/08/dont-waste-yo... http://blog.keen.io/post/29904565692/how-i-negotiated-my-sta... http://jacquesmattheij.com/first-employee-or-cofounder/

There are a few equity calculators out there on google, both for partners and early employees. They might give you some direction, although I wouldn't solely rely on them.

Good luck!