Hi I do mine in mid/late december.[I escape to the greenhouse on the 25th] I cut most of the stems back to about 3-5 clear buds [swollen sections on the stem by then.] I sometimes take stems back to the main stem but usually have about 4 stems for next year.

My grapevine is outside and about 30foot long. It gets taken right back to its rather gnarled main stem when the leaves are no longer the wonderful display they are at the moment. As Seaburngirl says you can leave buds. My vine is so vigourous, and still loaded with edible grapes, that our friend will probably have to come back in December to do the pruning rather than next week. You can take it back to a stump if you want. As in Vineyards.