Start with the arborists that are listed in the phone book. Don’t place much emphasis on the size of the yellow pages ad - some of the most reputable firms rely almost entirely on word-of-mouth advertising and use relatively small Yellow Pages ads. Look instead for what the ad tells you about the company: number of years in business, professional affiliations, licenses, certification, etc. Avoid companies that advertise topping, an injurious and unacceptable practice.

Seek recommendations from neighbors, friends or business associates who you know have had professional tree care work done in the past.

Check with your City Hall and see if the municipality requires licensing for arborists; many communities do.

Check for certification by the International Society of Arboriculture, or by a local certifying body such as a state arborist association. Certification is voluntary, and is an indicator of professional practice, but not a guarantee.

Pay attention to your instinctive feelings when you contact companies by phone as well as when they send a representative to look at your trees. Try to arrange a face-to-face meeting with the arborist when he/she first comes to your property.