I usually prune my grape vine Xmas day [its in the greenhouse] gets me out of the kitchen for an hour or so.

it should be pruned before the buds break in march [Jan or Feb is best]. cut down the long stems to a healthy bud. How far back depends on how much space you have and how much fruit you want. [I cut mine back very hard leaving only a bout 3ft height and 6-9" wide]and get plenty of fruit. then once it starts into growth don't prune as it will lose lots of sap and minerals as a consequence.

It is very confusing when they talk about rods, canes, spurs, cordons, etc. As mentioned, just prune it in the winter when the vine's dormant. I cut mine just above the second bud on the dead wood that comes off the trunk. These two buds will then be the new shoots for next seasons growth.