Always go with a certified arborist. These men and women adhere to a code of ethics, trim according to scientific standards and continually update their knowledge and training. This is opposed to joe-pickup truck trimming. Yes, they may be more expensive, but a tree is an expensive investment in your total property value. That said look to Baca, Bryan Suhr (you can ask Dodie for other arborists names as they stay in contact with ISA certified arborists.......I don't any longer), Scientific Tree care, Eric's Tree care.

If you go with joe pickup truck service, make certain they are bonded and insured, just in case a limb comes through your roof or the trimmer falls from the tree.

I use Landmark Unlimited; he has done our trees for years and is an artist with a chainsaw/pruners. He refuses to top a tree but instead climbs, prunes, gets down and stands back to survey and then climbs back up to prune some more. Not sure of his arborist certification- only the great results he gets and he really seems to know his stuff!