Inspect the potential vines for graft unions, the points where buds have been grafted to the vines. The graft should be flush against the vine. Gently bend the the graft to test its strength; if it breaks or shows a gap, it's not healthy.
Check the roots. Don't buy vines with withered, damaged, or discolored roots. Choose plants with the healthiest, fullest roots.
Check the bark on each vine. Don't buy vines with bark that is black, soft, or spongy. Black bark is a sign that the vine has a fungal infection.
Check the size of the vines. Buy vines that are around 1 to 1 and 1/2 feet long with at least six buds and have a width equal to that of a pencil.