Do they install their own work, with their own employees? Or do they subcontract it out to others.

Do they provide a warranty that warranties the installation, not just the pavers? (Most all paver manufacturers already have a lifetime warranty on their product.) How long have they been installing pavers?

Are they an ICPI certified installer? The Interlocking Concrete Pavement Institute is the only national association that certified installers.

ICPI has written the specifications for how pavers should be installed. Be sure your contractor is installing per ICPI specifications.

Have they been trained by a paver manufacturer?

What percentage of their business consists of installing pavers? Many landscapers have added paver installation to boost their revenues in a down economy.

Do they have a portfolio of photos to show their work? Can they provide references.