Ian,
I was not being secretive, it's just that the finer points are best demonstrated rather than described.
Here are, however, a few basic principals that should help:
Not all areas of any carpet receive the same soil-load or trafficing - under a sofa may require only a single pass wheras traffic lanes and shoe-shuffle areas require more attention.
A brushing vacuum cleaner will do its' best work on the draw-stroke, so quick foreward, slow back is the most productive approach.
The soiling which needs our closest attention is the impacted soil at pile-base and this is best removed with the pile vertical. Hense the draw-stroke should be against the current pile-lay.
In traffic lanes and other areas where the pile is flattened or tangled, pre-treatment with a stiff pile brush to 'open' and stand up the pile and at the same time break up the impacted soil prior the vac'ing is beneficial. Either a hand brush or one of the contra-rotating electrical devices will do this.
The vacuum cleaner should be delivering its' best performance - I have written extensively elsewhere of the importance of bag changing and brush maintenance.
There is more to it than this, but these are the basics on which to develop the technique.
Don't forget either the point raised by Alex concerning posture - many people pushing a supermarket trolley or a vacuum cleaner will hunch over and put undue strain on their backs. I have also seen many pro cleaners falling into the housewife trap of wasting energy by vigorously shuffling the 'oover back and forth at a speed that gives the machine time to do no move than pick up surface crumbs - use the electric energy rather than your own
John.