Ask HN: Tips/Tools for negotiating Salary at offer time?

Throwaway to protect privacy as the company has a decent amount of senior devs on HN.

I've recently been interviewing for a fairly senior position at 3 companies. All asked for compensation info up front before the interviews and I naturally declined until we see if things go anywhere.

I've now completed the interviews at 1 of the 3 and they are ready to make me an offer. They've requested references and asked for my comp requirements so that they can put together a "compelling package." I obviously would rather not disclose my current compensation first. Also, I work at a public company and I'm note sure they would appreciate me disclosing comp info for my position. How do I get these guys to throw out their offer first?

Also, this particular company making the offer is a startup that went public fairly recently (~2 Years) so not sure how to leverage salary vs RSU, etc. The other two are a Series B and Series C startup, do I mention to the others that I am about to get an offer? I am past the second round at those two.