I think it's really hard to determine if a maid is good or not until you try her out which is VERY risky.
Besides this if there is good recommendation from a trusted friend then probably she is good or from a trusted agency the likelihood of getting a good maid is higher but not 100%.
I guess things to look out for if you are getting one to care for your young one would definitely be PATIENCE. "patience is a virtue" with the crying and all PATIENCE is definitely needed.
Love for kids would be another.
But besides those hardworking, willingness to learn, caring and all will be good but it's impossible for all to come in one package so you will have to shortlist what are MUSTS and those you can close one eye to.
Lying, irresonsible, easily irritated, too smart is definitely a big NONO.