Most important of all is what will be reflected in your mirrors. You don't want to be always looking at yourself when relaxing on the sofa, and mirrors that picture you eating with friends — or worse, eating your breakfast — are a definite no-no.
In hallways, full-length mirrors work well, lightening, lengthening and widening the space, while a mirror between two windows in any room can give the impression of a third opening. Some eye-catching designs are divided into "panes" and arched, to heighten the illusion.
A chest with a lamp and an elegant vase on top and a well-proportioned mirror behind creates a feeling of space. Mirrors behind bedside tables can give the same effect. A mirror opposite a window will reflect light and a view, which is great news if the view is beautiful, sad if it's dingy. A mirror at right angles to a window does the same, and of course the view is different.
Mirrors in alcoves are a given and mirrors above fireplaces should be big, preferably covering the whole chimney breast, and finished off with a handsome bevelled edge.
Buying mirror from a builders' merchant, or a glass supplier who will cut it to your required size and will often come to your home to fit it, is a cheap way of creating great effect. And buying old picture frames for little money at junk shops or small auction houses, then fitting glass into them, works out a whole lot cheaper than buying an "antique" mirror.
If you rent your home and are not allowed to fix a mirror, lean a tall one against a wall — but make sure it is secure.
Round convex mirrors have an intriguing fish-eye effect, while a sunburst mirror is eternally splendid. Currently many artists are experimenting with mirrors to beautiful effect — find collectors' pieces at the Vessel Gallery in Holland Park, for example.