My Wisteria has gone mad - even despite cutting some bits off over the Summer.
It definitely needs pruning but how short should I cut it - and where?
It's probably best to wait a bit before doing anything drastic. When all the leaves have fallen it will be easier for you to see those points on the stems where next year's growth will begin, from new "buds". I think that most of us who have wisterias have seen a greater amount of growth than usual this year - mine have set more seed pods than ever. If you wait until the usual pruning time - February - you can then decide which parts you want to train and grow, and which you want to remove altogether.
If the plant is reasonably well-established, even if you cut it right back to what you might call "the trunk" it will most probably shoot from there too, even if there don't appear to be any obvious buds. You'll need to tie it to its supports and this is easier when there's no foliage to wrestle with. It's quite important to make sure that the roots don't dry out during the autumn & winter - most wisterias seem to be planted against a wall and the soil there is often dry and of poor quality, so some good mulch or manure will help a lot with the new growth when it finally emerges.
I hope this helps a bit - my wisterias grow like triffids all through the summer months, so I have to do regular tidying-up then, otherwise I'd not be able to see through my windows!
The RHS offers this advice - http://apps.rhs.org.uk/advicesearch/profile.aspx?pid=242
As you will see, there are two pruning sessions to keep a wisteria looking good. You may want to wait till Jan/Feb to follow the instructions for the winter pruning and then you do it again in July/August.