Styrofoam or Straw Wreaths 
Styrofoam or straw rings are available at most craft stores. They offer the advantage of a uniform shape for your wreath, and also make it easy to attach decorations with a wire or stickpin. If you use a styrofoam shape, you'll want to either cover it completely with decorations or cover it with ribbon or cloth before adding your decorations.

Wire Hanger Wreaths
Old wire hangers make a quick and cheap shape for making a wreath or swag. The disadvantage of the wire hanger is that you have very little support for your decorations. Bend the wire into a circle. You can leave the top attached to hang the wreath by, or use wire cutters to snip it off in the middle of the twist. Using needlenose pliers, open the twist and bend the ends back and down to hide the sharp edges. Try this project: A Hanger and Lace Christmas Wreath

Wire "Forms"
You can buy these at most any craft store. They have the advantage of a uniform shape like thestyrofoam shapes. Decorations can be secured using wire. Try this project: Christmas Ball Ornament Wreath

How to Make Grape Vine WreathsGrapevine wreaths are available in varying sizes at most craft stores, however, you can make your own if you have access to a grapevine.

Cut the vines from the plant as soon as the grapes have been picked and/or before first frost.

Cut long lengths so that you can wrap long continuous coils. Snip off remaining leaves. You can leave on the little curly-cues for a nice effect on finished wreaths. If vines dry out and crack or break whilewrapping, soak in water overnight. If you won't be able to wrap them right after cutting, coil them into a laundry basket, bucket or large tub. Then if soaking is needed, you can pour water right into the tub, and the vines will already have a coiled shape.

Begin your coil with the thickest end of one vine. Coil it into a circle a little smaller than you want your finished wreath to be. Use a short piece of wire to tie the first coil secure while you continue wrapping.

Wrap one entire length, twining the vine in and out around itself. Take the next vine - begin wrapping it in a different spot and wrap in and out in the opposite direction. Keep adding vines until the wreath is as thick as you want it. If needed, tie a short length of wire around the wreath at intervals to secure vines together.

I like to wrap my vines fairly loosely. This leaves me room to weave ribbons in and out of the vines easily, which adds a nice dimensional effect.

Tools to have handy:

Scissors
Hot glue gun
Thin wire
Wire cutters
Needle nose pliers

Decorating:
Wreaths can be decorated with a wide variety of materials, limited only by your imagination. As a general guideline, attach "background florals" to the base of your wreath first. Cover the base as much as possible. THEN add your small decorations.