1. Check references
An obvious but easy thing to overlook when you’ve got a million and one things to do.  Ask for contactable references so you can actually speak directly to the agency’s client.

2.  Meet them first
If someone’s going to be coming into your home, it makes sense to get acquainted first.  It will give you more peace of mind.  If you’re using an agency, request to meet your cleaner beforehand.

3.  Make sure they are certified and insured
Ask to see proof, including copies of insurances.  It’s important to know the company has good policies in place should anything go wrong.