The key to assuring the effort to check references is worthwhile and yields useful information is to request that your contractor candidate submit recent business activity.
You want names and contact information of their most recent clients with dates of service (that you will confirm). This is to prevent the contractor from “cherry picking” only his best customers, and attempting to ignore the weaker references and helps identify any gaps in the sequence of their projects that could indicate a less than stellar performance.
A gap in projects doesn’t necessarily mean a contractor is trying to hide mediocre references and could simply mean the contractor didn’t work during that period (good contractors, however, generally have a backlog of projects and tend to stay busy). We all know you can’t please all the people all the time, but it remains wise to seek an explanation for gaps.
The purpose of any reference check is to verify that the contractor is as professional and productive as they claim they are.
To that end, you want to determine what work they did so you may draw some inferences as to how well they might execute your project; spraying an exterior isn’t going to tell you much about how well they paint interior doors. Ask the reference whether there was any behavior that was questionable or lacking while working on their project. Did they arrive on time, work as budged, and finish as predicted? Were they neat and relatively unobtrusive? Were all the workers knowledgeable and polite? Were they safe? Etc.
The key question you want to ask every reference is whether they would use the contractor again. Is there anything they hope would be improved if they were asked to do another project? And, do they have any advice for you about using this contractor’s service?
Check a minimum of three references (most of us are sold after the first glowing reference). Dig deeper. Ask the same questions of each reference and listen for subtle clues that may indicate an enthusiasm variance from previous responses. Probe for more details.
We’re not digging for “dirt” with this exercise, we’re seeking truth. We’ve got enough to deal with just figuring out what we want to do, and how much it will cost without adding more stress with the possibility of a bad hire; better to make a fair and informed decision so that we can confidently proceed with our project. Verifying that the quality of execution is not likely to be an issue can be a great comfort when you’re in the thick of things.