This short video sequence shows you how to use crutches effectively.



In case you cannot see the video, here is a still sequence -

using crutches You need to take your weight on your good leg, while you advance both crutches and then the bad leg at the same time. Then you will be able to bear the weight through the crutches rather than on the bad leg. Keep your weight on the good leg and advance the bad leg and the crutches at the same time. 
using crutches Shift your weight over onto the crutches, then advance the good leg while your weight is being taken by the crutches. 
using crutches When using crutches you need to be aware of the terms 'non-weight-bearing', 'toe-touch', 'partial-weight-bearing' and 'full-weight-bearing'.

With non-weight-bearing, there is absolutely no weight taken on the bad leg - it makes no contact at all with the ground as you walk. 
using crutches With toe-touch, the toes of your bad leg are allowed to touch the ground to help with balance.
using crutches With partial-weight-bearing, some of the body's weight is allowed to be taken. This is usually a percentage of the body weight, such as 30%.