1. Hire someone who is bonded, licensed and insured. In some states tree service companies must register with the state, but that is no guarantee of quality.
2. Ask for references and get more than one bid. Take your time and select a company you know is reputable. Examine the credentials and the written specification of the firms who submitted bids and determine the best combination of price, work to be done, skill and professionalism to protect your investment.
3. Ask for a Certified Arborist, someone who has passed the International Society of Arboriculture's extensive Certification Exam covering all aspects of tree care.
4. Membership in professional organizations such as the International Society of Arboriculture (ISA), the National Arborist Association (NAA) or the American Society of Consulting Arborists (ASCA) demonstrates a willingness on the part of the arborist to stay up-to-date on the latest techniques and information.
5. Beware of door-knockers. Most companies have business cards, uniforms, truck signs, etc, and the reputable ones are generally too occupied to solicit work in this manner. Remember that improper tree care can take many years to correct itself, and in some cases never corrects itself at all.
6. A good arborist rarely recommends topping, and should try to talk you out of it if you request to have a tree topped. Avoid tree toppers at all costs!
7. Never allow a climber to use spikes or spurs to climb your tree unless the tree is to be removed.

The International Society of Arboriculture's Certified Arborists Directory lets you search for arborists in your local area and confirm certification credentials.

Also, see our Consulting Arborists and Commercial Arborists lists for selected Pacific Northwest arborists who provide varying consulting and commercial tree care services. Put a professional to work for you!