In almost all cases, you can have someone look at the work you are interested in having done without having to pay anything. This applies to most cases except for mechanics, they charge you for pretty much walking in the door.

The way to get a clear and precise quote from a contractor or company is to know what you want to be done. 
I remember a phone conversation I had with someone calling in to get a price for painting their condo. I asked them if they just wanted the walls painted or if there was anything else. They surprisingly asked "well, what else is there to paint?". I replied, "Ceilings, doors, door frames, window trim, baseboards, did you want the insides of the closets done?"

The clearer you are on what you would like to have a price on, the clear the quote will be.
If you want additional things priced along with the main area you wish to have painted, then let them know. The more specific you are at the time of the estimate, the clearer the quote will be.

What should you do once you receive the quote?
Review it. Make sure that everything that you wanted a price on, is on the quote. Does the quote mention who is providing the paint, what the painter will be doing to protect your belongs, who will be moving the furniture and putting it back? 

Other things to keep in mind when meeting with potential contractors or companies... 

- Do they have coverage; insurance, WCB?
- Are they part of the Better Business Bureau  and what is their rating on BBB?
- Did they come recommended or do they have great references?

One last thing, never pay up front for work when nothing has been done. 

Hope this helps in all your projects.