Childminders, like parents, will vary massively. You will find childminders who are equally 'good', but completely different. It's a very personal choice.
You need to think about what you want/what is important to you and work from there.
Food - do you need food provided? Would you prefer to bring your own? Does DC have allergies? Can the childminder cater to that? Does stuff need to be organic/particularly healthy?
Pets - yay or nay? What sort of pets would you be ok with? How would you want them to be handled e.g. contact with the children/no contact with the children.
Other kids - would you prefer other small children so that DC has children around the same age to play with or would you prefer mainly older children so your DC gets more attention from the childminder. What about the childminder's own children?
Driving - Do you need the childminder to drive? Do you want the childminder to drive? Who provides car seats?
Outings - is this important to you? What sort of outings? Would you be happy to pay more for playgroups/outings etc. or not?
Activities - is there anything that you would really value? An outdoorsy childminder? Sporty? Crafty? Very sociable?
House - is outside space important to you? Do you want a homely type environment or more of a nursery look?
The key is to know what you want from the childminder then you can judge if they're 'good' for you or not.