Here is a table of wire gauges and typical uses for the gauges. Use this as a guide if you're unsure which wire gauge to use.

14 - 16 gauge
Very thick wire, used as a frame or base for pieces that must hold their shapes such as napkin rings or bracelet bases.
18 gauge
Thick wire used with beads with large holes, making clasps or in projects that require stiffness. Also used in chainmaking.
20 gauge
Good general purpose medium wire used for making findings such as headpins and small clasps.
22 gauge
A light medium wire used for wirewrapping semi-precious beads and making thicker earwires or thinner headpins.
24 gauge
A thin wire used for wirewrapping small beads such as crystal and pearls, and making thinner earwires.
26 gauge
Very thin wire used for free form wrapping beads onto a base, or wire wrapping very small beads. Loops with this gauge need to be wrapped to stay closed.
Higher gauges
Higher gauged wires such as 28 and 30 gauge wires are used for free form wrapping smaller beads onto a base and wire knitting and crochet.

This chart provides descriptions and uses for various wire gauges. If you are unsure what gauge wire to use for your project, we have a technique tutorial on Selecting a Wire Gauge For Your Project.