Make certain they follow ANSI A300 pruning requirements and Z133 security requirements, showing industry best practices.
https://spark-wiki.win/index.php/What_to_Search_for_in_a_Tree_Company:_Rate_Openness,_Devices,_and_Tree_Trimming_Competence
Ensure they follow ANSI A300 pruning standards and Z133 safety standards, showing industry best practices.