taken from rhs encyclopedia.

they may be reluctant to flower unless vigorous leafy summer shoots are severely curtailed. flowering is also improved if the main stems are trained horizontally. flower buds are produced on short spurs. prune to encourage these along the framework.
2 stage pruning regime cut bacl long growths and shorter lateral growths. leave stems unprunned only if they are needed to extend the framework and train them in. in mid-winter cut back summer prunned spur shoots. at the same time, reduce to 15 cms 6" to me! any long growths that may have developed after summer pruning.

will try to scan and send the page if asked.

propagation. as a wisteria can take time before flowering they are best propagated by layering

The two pruning times are February and July or August. Assuming yours is already taking up the space you want it to, or more, then follow Maisiesdad's advice as to how to prune.