How many use a mirror? How has it helped? How often do you use it?
from
http://larrykrantz.com/chapt2.htm#flpf
The mirror is your best friend…It’s going to be able to suggest, point things out. Your development is always in the practice room and the more mirror you use [the better]. [You’ll see] problems of tension. If I tell you that you are moving, you don’t believe me. Why should you? You can’t see yourself. Seeing is believing, okay?
Larry Krantz is a great resource, ignoring all that stuff about tonging…
I often play while walking around the house doing various odd tasks. We’ve got at least one mirror in every room, and they always remind me to correct my posture. I tend to let my bottom hand drop and my head follows.
Nope, I don’t. Tried it, but I can’t get close enough to see much of use. even if I’m sitting in the sink.
Looks like few folks in this forum do mirror work. That is not surprising considering a good percentage play at session. (Not many Irish Trad bars around with mirrored walls 
.)
Since reading about the idea, I have tried looking at myself. I much prefer closing my eyes while playing. I haven’t decided if the mirror is useful to me, but it is something else that I can try.
using a mirror can be useful to check things… your posture, how you have the flute placed on your lips, what your lips are doing…
to have a good look it is handy to have one of those make-up mirrors, the bigger ones on a little stand that can flip and has two sides one of which enlarges things… the light coming from the back side of the mirror gives you the best results to see what you are doing.
so you can place the mirror in a windowsill and stand in front of it.
it comes in handy to check if you are not sounding properly and cannot find out why, or when you get a sound you like a lot and then you could look at what the lips are doing…
I find playing in front of a mirror now and then does help to get things work better, especially if you are still a beginner.
If this still goes when you are an experienced player, cannot say, have to find out the next few years
berti
I’ve used a little one in the past for peering at my embouchure, and still do occasionally if my tone is sounding strange to me. I can sometimes find the problem that way, or eliminate one possibility. A full length mirror is good for posture. And if you stand close enough to it, it reflects your sound back to you very nicely.