As a rule of thumb, most homeowners should not attempt to fell trees larger than six inches in trunk diameter. To find a professional tree service, check the phone directory under “Trees,” “Tree Service,” or “Tree Care,” though anyone can list themselves in the yellow pages. Beware of “door knockers” and pressure tactics such as “if you sign an agreement today...” Ask a prospective tree service for local references and verify them. Determine if arborists are certified by the International Society of Arboriculture (ISA). You can also check the ISA Web site for certified arborists in your area at www.isa-arbor.com/findArborist/findarborist.aspx. A “licensed arborist” may just mean the person has a business license. Also, contact your Cooperative Extension office or state division of forestry and ask if a list of qualified tree services is available.