The decision to change your bathroom mirror shouldn't be taken lightly. These mirrors tend to be large and require installation with secure brackets and, in some cases, adhesives. In other words, repositioning or changing the mirror once it's installed isn't the fastest job, even for professional installers. That means that you and the installer need to agree on where that mirror is going. When you speak with the installer, be sure you're on the same page regarding the following considerations.
Perpendicular to Medicine Cabinet Mirrors
It helps anyone who is getting ready to be able to see the back of their head, and one of the easiest ways to do that is to have two mirrors that the person can position. If there is a medicine cabinet with a mirrored door in the bathroom, place the new mirror so that it is perpendicular to the cabinet's mirror. Your old mirror was likely in that position anyway, but if you were thinking of changing the layout, or if you've remodeled your bathroom, keep in mind that there was a reason those two mirrors were so close together and at that angle. If there's no second mirror in the bathroom, install one of those telescoping mirrors that you can push back toward the wall when you don't need it.
Watch the Height
Very large mirrors, like the flat, frameless plates you see in a lot of apartment bathrooms, are very tall and wide, making it possible for most people to see themselves no matter their height. If you are installing a smaller mirror, particularly one with a frame, be sure that both short and tall people can see themselves. You can't plan for every height, but you don't want to place a mirror so high up that only those over 5'5" can see their entire faces, for example. Nor do you want it so low that anyone over 6 feet has to squat down. Odd mirror heights could affect home resale possibilities; even if a mirror can be changed, it's just one more thing the new homeowner would have to do and that can make your home look less appealing to buyers.
Keep Frame Type in Mind
Remember that frames and beveled edges on the mirror reduce the usable reflective surface. Planning the installation by measurements only may mean that taller members of the household find part of their head blocked by the frame or decorative edge. Frame type also influences where the mirror goes in that frameless mirrors are often installed right at the counter (i.e., no space between the counter surface and the bottom edge of the mirror), whereas framed mirrors may be hung higher up.
These aren't the hardest decisions to make, so don't be put off by the need to discuss this information. Getting the mirror placement right is worth the time it takes to ensure you and the installer agree on all questions. Look for a bathroom mirror installation company like Econo Glass Systems and ask their staff for assistance.