Short answer: Good trimming removes problem limbs over roofs and driveways with clean cuts just outside the branch collar. It never means topping the tree. A local contractor can tell you whether trimming is enough or the tree should come down.
Common trimming jobs
- Limbs over the roof that drop debris or scrape shingles
- Dead wood that could fall in the next storm
- Clearance over driveways and the house
- Thinning crowded trees to let in light
What good pruning looks like
Cuts are made just outside the branch collar, not flush with the trunk and not leaving stubs. "Topping" (cutting the top off a tree) weakens trees and often causes more hazardous regrowth. Avoid contractors who recommend it as routine.
Power lines
Branches touching service lines or utility lines are a job for your electric utility or a line-clearance-qualified crew. Call your utility first.