Sometimes the best way to break a stalemate over equity is to agree on equal shares but give someone a faster schedule or some portion vested up front — or, conversely, agree to allocate a larger percentage but tie it to a longer vesting schedule and/or milestones. Shares aren't really "owned" until they're vested.

There's no hard and fast rule about vesting any more than there is about exact equity percentages, yet entrepreneurs often assume everyone's shares must vest according to the same schedule. Instead, I recommend taking a hard look at past, present, and anticipated future investment of "sweat equity" in the venture by each co-founder. More often than not, in my experience, someone started working first/harder/longer, quit their day job, made a critical breakthrough early on, etc. — or is expected to pull the most weight in the coming months, solve thorny technical problems, recruit vital team members, and so forth. (Yes, it's a guesstimate, but the same is true of valuation and almost every other metric at an early stage startup.)