How do you trim a grapevine for winter?

How do I trim a grapevine to be ready for winter and next spring?
I know there is something special I should do, but have no idea.

please follow a step by step expert's guide http://www.ehow.com/how_2079844_care-gra...
I hope it helps.

Put a stake in the ground and pull up the vines and tie them gently to the stake. Trim off any extra that goes above the stake. Make the stake at least 3 feet tall out of the ground. I have read some publications that save just prune them to four strong branches. I've seen it done the way I first told you and they look marvelous in the spring.... your choice. Good luck!

It depends what area you live in normally wait until after Dec. 21, two reasons;
1) All leaves are or should be off vines and the frist Frost should have set in to make the leaves all be off vines.
2) Now are you raising your Grapes for personal eating.
a) If your growing for personal wine making matters also,
how you are going to cut them.
3) Here is one of several ways to cut depends on what you want: High sugar content or for Better wine Grapes:
Now high sugar content as I was trained by Old Wine Grower that taught our class over 35 years ago
As you look at your vines shoots growth you shall notice small bud likes items on the branch. These are your growth areas for next season. So now as I mention above if you want High sugar in the grapes. You start a count from last season nodule Bud- this one shall have a strong wood stem-ring around it then another Bud- start your count as one bud to next one. Then as you get to a even Bud count:
[ Example: 4,6, 8,12 etc. Now cut this at a distinctive angle cut,then tie this vine with either Green tie tape to a wire or or wood trellis. Then around the base or Roots stock apply Sulfate Ammona around in the Early spring-Jan-No Later then
Feb.20 the reason for this nurishment High amounts Nitrogen food to the Plant growth. Now the other way for better Wine Grape is Odd count from the Buds: Example: count 5,7,9,
13 then cut again same as above. Now same method of tie again. However if you rater there is other forms to grow and train if you wish to research those get a Copy from Sunset-Garden Books, or Ortho Books of prunning from Roses to Garpes. Now there is three other ways to prune Grapes and train them I have just stated the most easy one . That is more practicle for Back Yards or a Patio area. So Good Luck Happy gardening to You. Landscape Contractor in Northern Ca. Pruning Expert over 35 years: [ Trees, Shrubs,Roses,Yes Grapes also.]

Do not trim until after the winter. Let the frost and freeze kill it back. If you trim it back now when the winter comes the frost and freeze may kill it. This will sound weird but think of your outside plants as a human body. As it is now the cold will kill off the arms but leave the main body, but if you take away the arms now you will only leave the main body for the cold to attack.