i'm quite new to this myself but here is what i've been told by my greek and albanian neighbours (either side) and they each had vinyards at home.
roots must be outside because frosty weather/snow is what makes the fruit sweeten.
each year in winter prune back to three 'knuckles' from the previous years (woody) growth on each branch. (the knuckle being leaf joints)
in late autumn make sure that no dead leaves or shrivelled grapes remain on the vine or in the dirt below. mummified grapes give off a gas that grows a mould and this mould can kill the lpant, especially in a greenhouse.
ensure that the vine has sufficient airflow throughout the winter to deter mould also.
try not to break any woody stems if not in the dormant season as the plant can 'bleed' to death :o
hope this helps,second hand advice tho it is, ;D
Tara xx