[AjariBonten]

While a lot of what you might really want to know is intangible, (ie: will we work ok together), there are some tangible indicators you can look for.

I suggested to the "captain Ron" I think you might be referring to in another thread some of the things he might provide to potential crew.

Among those might be:

references
survey of vessel in question
proof of insurance
a written and realistic passage plan (researched, pilot charts, expected weather & conditions, time-table)
A written list of expectations and responsibilities.(this can be as complex as a contract, or as simple as a checklist, but should include such items as watch schedule, provisoining responsibilities, list of duties, personal declarations, such as no smoking/drinking/snoring, LOL) I think you get the point.

None of this is any guarantee; but a good plan and preparation is a good indicator of seriousness and possibly competance.