Home improvement: pick the product, then the contractor.

Roughly 75 percent of homeowners choose their own exterior house paint and stain, thanks in part to decades of consumer advertising. But when it comes to asphalt roofing and vinyl siding, most people still let their contractor choose.

Significant performance differences in our latest roofing, siding, paint, and stain tests suggest that you, rather than the contractor, should decide what goes over and onto your home. Increasingly, manufacturers and retailers are making that easier by providing installers as well as products. Some manufacturers and retailers may reduce the risk of shoddy work by screening and even certifying installers. According to the National Association of Attorneys General, home-improvement contractors elicit more complaints than all businesses except auto businesses and phone companies.

Industry associations such as the Vinyl Siding Institute are also raising the bar for installers. The institute currently offers training programs and is developing an installer certification program it hopes to implement next spring.

But as the tables below show, product choices and installation services vary depending on where you shop. And while the major retailers have satisfactory track records with their local Better Business Bureaus, most aren't free of complaints.

Here are some of the installation deals you'll find, along with what you can do to locate and screen home-improvement contractors on your own:

Manufacturers reach out. Roofing and siding companies such as Certain-Teed, GAF, and others now help you find local contractors who have been trained by the manufacturer to install its products. Some offer certification programs that require training, experience, licensing, and insurance.

Retailers raise the roof. The largest, Home Depot, began using outside contractors to install roofing and siding five years ago through its At-Home Services program. The retailer covers one or both products at more than 1,200 of its roughly 1,570 stores through exclusive agreements with pros. It also guarantees the work beyond the product warranty.