It may seem cheesy and somewhat simplistic at first, but after you get over the cutesy anecdotes and jokes, the book/method "Slicing Pie" by Mike Moyer has been

It may seem cheesy and somewhat simplistic at first, but after you get over the cutesy anecdotes and jokes, the book/method "Slicing Pie" by Mike Moyer has been a very helpful resource for me during several very early-stage bootstrappings. It really helped contextualize the different types of contributions co-founders and early employees will bring to the table, and is a helpful transition into the world of stocks and equity for those who are less familiar. I bought copies for all involved and we worked through the calculations together, resulting in equity splits that have so far been low-drama.