I want to ask a calligrapher to write something, but I don't know what is appropriate for him to write. Please give me some advice.

If you are a calligrapher, you don't have to tell him what to write. It's a piece of cake for calligraphers. Don't even know what to be a calligrapher. In addition, let the calligrapher write by himself, usually he will write what he is good at. If you let him write what you specify, maybe he can't write well. This is very possible, haha. However, if you want to hang it on the wall, you might as well write some words that suppress evil. Nowadays, the social bad style is too heavy, and pressing it is good for your health and destiny.