It's important to strike the equity deal in such a way as to create incentives for your actual objectives.
There is a huge, huge difference between giving someone a little equity spiff in lieu of cash for professional services (e.g., a professional designer friend who helps you out with a few design elements) and giving someone an incentive to become your co-founder.
Assuming you're talking about the latter type of contributions, I would point out that in general, doing a startup is really hard. Most people can't contribute meaningfully to the success of one on an "on the side" basis.
It's kind of like a rock band maybe -- are you in for the jam session, or are you bailing early because you have somewhere else to be in the morning?
Putting it another way, the opposite of what you want to do is give people an easy way to not quit their jobs to join you f/t, instead giving them a lot of option value if you succeed without much skin in the game if you don't.