One of the most important things to learn as a homeowner is how to look up a potential contractor and more importantly to trace back through name changes etc...
There are several things to look for when checking out a license or company. On the contractors license board website, there some links that appear or not appear depending upon the license searched.
Besides the normal stuff like, do they have worker comp?, any disciplinary actions?
look for "other licenses", look at the personnel list and click on their names to see if they are associated on other licenses.
If you find other licenses look at those licenses, the business name used, the owners name, and then look all of those up on the better business bureau.
At the Better Business Bureau check the owner name against the owner name on the contractors license. Some companies simply use a contractors license as long as it remains good, if they fowl it up, they simply find another contractor with a good license#
Another thing to check for are the addresses and phone numbers listed, are they consistent in the company's advertising, license information, and better business bureau record?
If you find any inconsistencies or if there is any questionable information, it is most often best to look for another contractor.
Keep in mind, the best contractors are always busy, so be patient and be ready, you won't be sorry.