Great advice here already. If you are hiring direct, do the background checks. I would also ask for references. Can you call their last three employers and see how things went? Also, observe how they are with your PALS. I turned down a couple of possibles who actually walked into the house, and then into my husband's room, while texting.
Strength is important, not only for the caregiver, but also for you PALS. We had to pass on a couple of people (including one nurse in the hospital) who just didn't have the physical strength, so they had to jerk my husband to move him. That was painful for him. I loved having big strong male nurses!!
Have cameras up in his room and in public spaces in the house--including where the meds are. If that's a problem, pass. I seldom checked mine--just the fact that I could mattered.
Have a written schedule and list of tasks for them to read. That's the best way to make sure you are on the same sheet of music. Your idea of caregiving and theirs might be different, and you need someone who will do things your way. Observe them as they read, and ask a few questions about their experience or understanding of the tasks.I f they can't read and follow instructions, you may have a problem. Yes, invite suggestions, but they don't get implemented without your (or your PALS) approval.
Don't get discouraged. We had a nursing agency for 9 months and they were never able to staff us with 5 people at the same time. I rejected more nurses than I approved (with my lead nurse's concurrence). Once you do find good people, treat them very, very well. They are going to be in your home performing very intimate tasks--if they don't feel like family it will never be comfortable. I was amazed at the stories I heard about how some families treat home heath care workers.