1. Agreed with tptacek. 1% is within the "standard" range of equity from what I've heard in SV. But that range is highly variable: 1-5%, but even 0.1-10% might be justified. But we have nowhere near enough information to judge whether that kind of an offer is a good offer for your specific, individualized case. Some questions to consider: What kind of salary are you making? What salary could you make at a BigCorp? When was their last round of funding, how much did they raise, who did they raise from, and what was the valuation? What kind of shares were issues to the investors (preferred, participating preferred, bla bla bla etc.)
2. Approach this like an investor. You are "investing" a below-market salary (and, if you are going to be working longer hours than at a BigCorp, you have to factor that into your calculations), and in return you are getting equity. The easiest way to calculate the dollar value of your equity is valuation * equity (then divide by four since this is vested over four years), and that is the rough cash equivalent of your equity). But depending on what kind of stock your investors got (preferred stock vs. the common stock or stock options you get), you might want to discount this valuation by 10-20%.
3. Valuing startup equity is a huge topic, there are entire HN threads dedicated to this: search HN for "startup equity." Here are some good articles: http://mba-mondays.pandamian.com/tableofcontents/ (read the Employee Equity sections), pg's essay on this (http://www.paulgraham.com/equity.html), an article on someone's negotiation process (https://keen.io/blog/29904565692/how-i-negotiated-my-startup...), and another summary article (http://www.payne.org/index.php/Startup_Equity_For_Employees).