Hello. I so feel for you & wish I knew someone in your area to recommend. I am currently in my 3rd year as a child care provider but first was a Mom in your position, searching for just the right caregiver for my children.
I would certainly suggest starting out making a list with your husband/partner as to what is important to you in a child care provider; a great checklist to go by in interview. A lot of things can be covered in a phone interview beforehand (perhaps weeding out some to save you time?).

Some ideas: First Aid/CPR trained? Criminal check? View sleep areas/outdoor & indoor play spaces....safe?...vi ew menus & discuss what a typical day looks like (is it a good blend of structured activity vs. free play, for example). Are there smoke alarms, safety plan, fire extinguishers in place? How does the provider communicate/what level...does this match your need? Ask how many children are currently in care (do they plan on taking more on?). Take the contract home and review it carefully before signing.

As for a trial period, I leave this up to the comfort level of parents...I am open to whatever parent & child needs for reassurance.

Hope all of that helps!