Most schools of thought have to do with valuation, compensation, and commitment but I've found that those "hard" considerations of an early cap table fail to really establish the value and passion of the core team. The way in which early equity is handled (not just share but cliff and vesting), speaks to less tangible values that the company is establishing. Here are some thoughts
on what to consider with regard to the stage of the company, the role of the individuals, and how much (or little) they are valued.
I want you to first ask and answer that question by warping your perspective of the term “investor” for a moment. I’m not asking you if your co-founder and employees are indeed investors, I’m asking you if they are investing their time in your venture. How do you perceive their contribution?
All that said, if you want a more practical and tangible way of addressing the issue, along the lines of Tomas' suggestion of Slicing Pie, consider using the Startup Equity Calculator