You can use a DPDT (Double Pole, Double Throw) SW in your guitar wiring in many ways. You can base on this thing many kinds of tone switches. You can use it as a pickup selector. It can switch coils in your guitar pickups (series/parallel, split humbucker, reversed phase, on-off etc.). It's also a good part to make a switchable signal bypass or a loop.
This diagram will show you DPDT connections in a few, popular examples:
As you can see, push-pull pots also have a DPDT switch: ON-ON.
Versions with a toggle are the most popular. You can get them in many sizes and types (on-on, on-off-on, on-on-on). Some models are very heavy-duty.
Here are some examples of how I used this things in my guitar wiring projects:
Direct-Through Strat Mod (bypass)
On-Board Effects Loop Control
Custom Wiring for Explorer, Flying V, ML, Razorback (pot selector)
Dick Dale Stratocaster Wiring ('bridge+middle' pickup activator)
George Lynch's Guitar Pickup Selector
Gibson Les Paul Jr and SG Jr Wiring Mod (tone switches)
Treble Bleed Switch
Simple Guitar Wiring With No Pots (phase sw, "on-off" pickup selector)
A DPDT switch can by a part of a really handy guitar tone control. These with toggles are more heavy-duty and more comfortable, but they cost some extra place in a guitar body. Push-pulls are usually less handy, but you don't need any extra places/holes to use them - you just need to swap them with your old pots.
