Lui

One of the most important things to remember I think is that most people don't like their trees touched. And it's funny, cause sometimes the tree will give you the wanting. Just try to restrain yourself unless the owner says it's fine.
I own a Portulacaria that has probably been touched by the entire population of Miami it seems most people see the shiny tiny leaves and think the tree is fake and they need to touch it to make sure it's real.
I agree with what Ron says nowadays people are more concerned about finding the defects in the trees than the overall beauty of the composition.
Oh, and another saying that works: if someone hears you say there something you don't like about a certain tree, you can say it's because it's not part of your collection.
Cheers
Lui