Farming may be what you know best, but hospitality is the business you are getting into if you offer a farm stay. It's not that hard if you remember to treat guests the way you would like to be treated if you were visiting an unfamiliar locale.
If dealing with customers is not your forte, find someone on the farm who enjoys talking to strangers, educating about farming practices...and has the time to spend with your guests without getting harsh looks from those doing the sweaty work. This is just as important because happy guests tells their friends about you and that is worth more than any marketing dollars you will ever invest in your business.
A number of universities have written about hospitality on the farm so instead of repeating what they say, take a look through these. There is a little repetition but that's a good thing!
UC-Davis Small Farms Program: On-Farm Customer Relations
Cornell Cooperative Extension: Customer Relations
Tennessee Cooperative Extension: Customer Service
Christina at Rinconada Dairy in California. Great smile for guests!