Step1
Figure out what you want to plant and where you want to plant it. Small plants with dainty tendrils will require lots of close together trellising to hold onto and climb. Large, vigorous climbers, like squash and gourds, need something sturdy and less closely spaced together.
Step2
Pick your material. Tree branches are an easy and inexpensive material with which to make a garden trellis, but you can use anything. Dig through the basement, attic or garage for old bicycle wheels, laundry drying racks, old rakes, rose trellises, scrap pieces of wood and other items.
Step3
Determine the size of the area where you want a trellis. Measure the width of the area and how high you want the trellis to be. Keep in mind how tall the plants can grow, so make sure it is tall enough.
Step4
Lay out your materials and determine how best to fit them together. Make a sketch of your design to help guide you, but improvise as needed.
Step5
For cobbling tree branches into a rustic trellis, hammer or screw the main supports and joints together for stability. For small lattice work, use small nails or garden wire. Small saplings that bend well work best for lattice work, but use anything that works for you! Soak branches in water to soften them a few days prior to using them.
Step6
Whatever materials you cobble together, consider the support issue. For stand up trellises, dig a hole to sink your main supports into. The weight of the vines may pull the trellis over, so make sure the supports are in the ground firmly.
Step7
An easy to way to maintain support is to leverage two trellises against each other in an upside down "V" shape. You still need to anchor the supports into the ground, but as long as the trellises are firmly against each other (steeper angles and firm connection at the top), you'll be fine. A good example is two garden rakes meshed together at the top with their handles firmly in the ground. Run additional branches from the ground to the rake tops. Try two old rose trellises put upside down at an angle and secured with wire at the top. Add branches or extra wood if the plant grow higher than the trellis "tops" (bottoms).
Step8
Modify your design as needed. Plants grow and expand beyond our expectations sometimes, so cobble together additional parts to your trellis when you need it, just make sure the addition is stable and will not compromise the strength of the rest of the trellis. Have fun.
Step9
Re-evaluate your trellis designs each year to determine what worked and what didn't. Determine what you could do to make something sturdier, taller, bigger, etc.?