Ask HN: How to negotiate compensation as third employee/CTO?

I've been talking with an early stage business about coming on board as their third member and only technical member on the team. They recently raised about $1m from angels, have some revenue and a decent MVP. I've worked for several startups in the past but never at this early of a stage where equity is most of the compensation. I'm curious if the HN community has any tips for negotiating compensation. All input considered and appreciated. Thanks!