I find it best to get people who are compatible in terms of personality and worry about sailing skills later -- unless they just have no boat sense, which is another issue.
After someone showed up onboard for a 3 day sail toting a blueberry cobbler (I mean, where do you store a blueberry cobbler?) I decided to post a set of crew instructions. They cover what to bring, what not to bring, some basic expectations, a little safety info, and so on. Some of them are a bit tongue-in-cheek but in general they provide useful info.
They can be found at
weathergage.com under "crew and guest instructions."