A little preparation goes a long way
What to include in your estimate request
The more clearly we can picture the project, the more useful the estimate will be. You do not need to know every mounting detail. A few practical notes are enough to start the conversation and avoid surprises later.
Share the approximate width and height of the mirror, where it will be hung, and whether you know the type of wall. If the mirror is unusually large, very heavy, or needs to be placed above furniture, mention that too. A photo of the mirror and a photo of the wall can be helpful.
It is also worth noting any nearby work that would make the visit more productive. Maybe you have artwork waiting in the same room, a curtain rod to install, a shelf to hang, or a few loose handles that have been on the list for months. One clear list makes it easier to see the whole job.