The first thing that I would suggest is to clearly define and understand what it is you want done. Sit down and think about your project. Write it down and list any important details. For example, if painting a bedroom list that the ceiling and walls will be a certain color and sheen, trim a different color and sheen, closet should be painted along with the shelving, both sides of the door, protect the glass on the windows and hard wood floor, etc. For a plumber or electrician list that if they puncture or remove any wall surface that you want them to make arrangements to repair it afterwards and here's one that I find particularly annoying, clean up the messes daily. Many contractors only want to provide the service they are trained to do and leave repair and cleanup to the home owner. This is not "ok" in my way of thinking. I can see some daily mess if they are in the middle of a repair but when the job is done it should be restored to previous condition. If they don't do drywall or repair work they should at least be able to recommend someone to come in and let you know that you will need to get another bid from other trades to fix the damage. This list will clearly establish your expectations and in writing communicate them to any potential contractor.
I know this seems overly precautious to some but "contractor remorse" occurs after the work is done not before and usually any post-job unfulfilled expectations are dismissed by the contractor as not part of the scope of work. In my business I submit an estimate with the scope of work clearly defined and when the customer accepts and signs the estimate it is a contract or agreement that is clear what will be done including clean-up. I am constantly perplexed at how much work gets done without a signed agreement or contract.
The Next step in finding a good tradesperson would be to check their legitimacy. Are they registered and insured? Check them out and ask for their insurance certification sheet. Some contractors will ask for a percentage of the job up front as earnest money. This is ok however, one should at least check the validity of their company by asking for references, documentation and have a signed agreement and an established start date for the job. Some companies will never ask for earnest money and some will ask only if it is a large job that requires a lot of material and will take a long time to complete. They might ask for progress payments if this is the case. Find out if they accept on-line payments or credit cards this is not only convenient for you as a customer but may be a good indicator for the legitimacy of their business as well. These things should be established up front before the job starts. I am also perplexed when I submit an estimate with a clearly defined scope of work to a customer that tells me "you got the job" and they balk at signing it or at least an email response to my documents as an electronic signature. This makes me wary of the customer's intentions. There are unscrupulous people on both sides of the fence.
Now, the previous paragraph leads to this next subject which can be a sensitive political hot button. When I was referring to legitimacy I was not talking about documented or undocumented foreign-born workers. There are at least 20 million undocumented workers in this country working everywhere from McDonalds, carwashes, hotels and the list can go on at infinitum. Most of these undocumented workers have a TIN (Tax Identification Number) and pay taxes without compensation and the benefits that documented workers get. Many of them also have legitimately registered businesses and licenses and do great work. However, be wary of the 2 guys a truck and a ladder that offer to paint your house cheaply. Hiring these guys is a gamble. Fist of all they may or may not do a good job. They most assuredly have a motivation to cut corners. They will not offer anything in writing and won't want to sign anything you have prepared either. They may or may not ask for up-front money but if they do please do not give them any. They aren't interested in building a brand or reputation for their business they are just living job to job and most likely do not have any insurance so if they get hurt while working on your house they can sue for damages. I know the price will be attractive but it might end up costing a lot more in the long run. Any legitimate business will at least have a website you can check out or a listing of some sort on the web and at the very least an email address where you can communicate with them.
As always I hope this was helpful in your considerations for a painting contractor.
Jay - Adirondack Painting LLC