Situate trellises along the north side of your garden to prevent shading other plants.
Anchor your trellises to protect them from the wind and to handle the weight of the plants by sinking trellis posts 24 inches deep.
What can you grow vertically?
Trellis nonbush or indeterminate types, which keep growing and producing fruits until frost. (Determinate varieties are often bushy.) Check out this plan for a sturdy tomato tower.
Grow nonbush varieties on trellises. Bush types don't need trellising; their vines reach only 4 to 6 feet long.
Pole beans, Gourds, Melons.
As a general rule, any variety with fruits smaller than a volleyball can be trellised. Vines will grow strong enough to hold the weight of the fruit, so there's no need to support fruits with individual hammocks.
Squash and pumpkins.
Small-fruited and nonbush types, such as miniature pumpkins, and acorn and buttercup squash, are suitable for trellising. Here are plans for a simple squash trellis.
For more vertical gardening ideas, check out Derek Fell's book, Vertical Gardening.