Moss Brook Growers has an amazing resource: an online farm manual, compiling their thoughts from years farming. Check it out here!
Here is a sampler from Section 6, "Recruitment and Labor": an extended discussion of how to keep an eye out for happy, healthy, and dedicated farmhands. And for farmhands, a model to aspire to!
Some of the more tangible and quickly identifiable attributes we were looking for are:

• speed of work – e.g. how many kg harvested per hour, or how many metres of crop rows hoed per hour
• thoroughness of work – e.g. quality of harvested crops, thoroughness of weeding
• practical / logical approach – e.g. working with machinery, thinking through problems
• prioritising jobs – e.g. what crops to work on first
• time management – e.g. fitting all necessary work into a day, not being late for customers
• good with numbers – e.g. writing invoices, crop planning
• IT proficiency – e.g. crop planning spreadsheets, record keeping
• ability to listen, learn and communicate – essential to working in a small team
• driving licence – preferably clean!

Continue on.
and check out their entire farm manual, too!