[Retric]

As a non founder think of it in terms of what your (worth to the market - what they actually pay you) * risk your willing to take. So if you can get a job at Microsoft for 110k + 25k in benefits, and the start wants you for 70k + 15k in benefits then your giving up 50K in salary per year and you need to get enough shares (which are probably worthless) to make up for that * the number of years it takes you to vest.

As a yardstick I would aim for 1.5x the rate of whatever the last round of investment was. AKA if they got 5 million and your giving up 50k then look for 10% of whatever the investor got vested over 3 years. (Also, the further from your market rate the shorter your vesting schedule needs to be.)

PS: Don't forget the idea is paying you in stock needs to be more expensive than paying you in cash or they are going to want to pay you in as much worthless stock as possible.