Some of the things that were important to me in looking at childcare in someone's home were the following:
1) Who else is in the house during the day while your child is there? One lady had her 20 something sons in and out all day with their friends - there was no way I was leaving my son there.
2) Does she take the children somewhere in her car during the day? I personally didn't want my son to spend his days in someone's car while they ran errands nor did I want him pushed in a stroller around the mall. This is more common than you might think.
3) If the caregiver is not available or has an emergency (or doctor appt, etc.) who is their backup, if any? My MIL's neighbor does in home childcare and she frequently has my MIL stay with the kids while she runs errands. I would personally not appreciate that situation for my own child.
4) What types of food are served and are they willing to serve your child food your bring from home? Where is the food served - i.e., does she just rotate each kid in the same high chair or does she have multiple? How clean is the food area?
5) Where do the kids spend most of their time? The room one lady showed me had small windows and the carpet was old. Personally, I don't think carpet is healthy and I'd much prefer my child in a room with floors that can be (and are) thoroughly cleaned regularly.
6) Does she have a dedicated diaper change area and what are the sanitary practices for diaper changes?
7) What are the rules for sick children? Will she accept them or does she require they be symptom free for 24 hours (i.e., throwing up, temperature, etc.)? I remember one mother when my kids were in daycare that followed that rule to the minute. If her son was sent home at 1:22 the day before, she'd have him back at 1:22 the next day. So, you cannot count on parents being responsible, so the daycare provider needs strict rules.
Also, I strongly recommend you trust your instincts. Unless you feel 100% comfortable with the caregiver and the environment, I would look elsewhere. In the end, I found that daycare centers often have a higher caregiver to child ratio and there's always someone around.
No matter what references you get, I highly recommend you run a background check.