Assume a putting stance.
Glance back at the mirror to see
the reflection of the string. Align
yourself untill you can only see only
one line.

You are now in a vertical plane with
the string (putting line).

Place the golf ball anywhere
from 6 to 48 inches from the mirror.

Ensure the ball is centered
below the putting line.

Reassume your putting stance in relation to the ball,
by glancing back at the mirror, and making certain
that you can see only one line.

The string should be obscuring
it's own reflection.

Look at the hole along the length of the string (putting line)
in order to get a feel for the distance (weight)

Look back at the ball and take the putter
straight back along the putting line.

Stroke the ball with a smooth,
pendulum-like putting stroke,
keeping the putter face square