If you're like most people, you will follow the most casual of recommendations for hiring a contractor, such as so-and-so rebuilt a friend's cousin's neighbor's deck and did a beautiful job, so he'd be perfect for your bathroom renovation.

You're ready to invest tens of thousands of dollars on a project. You've spent months looking for the perfect fixtures. You've lost whole weeks pouring over plans. But are you ready to award the actual work — the fruition of your project — to someone whose credentials you've hardly given a second thought?

This blind spot probably results from our overwhelming ignorance of what contractors actually do. We are so awed by their purported skills that we rarely bother thinking about details. Or perhaps we don't consider the skill of a contractor at all: imagination and expertise come into play only during planning and preparation; once the materials are chosen and ready, all the contractor has to do is follow a recipe, right? 

Actually, hiring the wrong contractor can be an extremely costly mistake. Unfortunately, finding a good one isn't easy, which is perhaps another factor that makes us latch onto the first name that comes along. While recommendations from friends of friends provide a start, your search shouldn't begin and end there. Be sure to follow other routes, as well:

• Consult national and local trade associations. The San Francisco Builders Exchange, (415) 282-8220, and the Marin Builders Exchange in San Rafael, (415) 462-1220, provide an online list of members, searchable by trade. All exchange members are licensed contractors. You should also visit or call the National Association of the Remodeling Industry (NARI), (800) 611-NARI (6274).