Safety first:

• When applying pressure to pliers, make sure your hands aren't greasy, otherwise, sooner or later, they're going to slip.
• Select the right type and size of pliers for the job. As with most tools - if you have to exert almost all your strength to get something done, then you're either using the wrong tool, or you're doing it incorrectly.
• If the pliers lets go, you're going to get hurt. At the very least you'll damage the tool, and the work.
• Pliers get a lot of hard use in the workshop, so they do get worn and damaged. That makes them inefficient and even dangerous. Always check the state of all workshop tools on a regular basis.

Combination pliers are made from two pieces of high carbon or alloy steel. They pivot together so that any force applied to the handles is multiplied in the strong jaws.

Some pliers provide a powerful grip on objects, others are designed to cut. Combination pliers can do both - that’s why they’re the most common type.

There are two surfaces for gripping flat or rounded objects, and two pairs of cutters. The cutters in the jaws should be used for softer materials that won't damage the blades.

The cutters next to the pivot can shear through hard, thin materials, like steel wire or pins.

Most pliers are limited by their size in what they can grip.

Beyond a certain point the handles are spread too wide, or the jaws can't open wide enough, but these multi-grips overcome that with a moveable pivot.

A pair of multi-grips can get a comfortable grip on a range of objects, and there are two surfaces for things that are flat or round.

Vice grips are general purpose pliers. Put an object between the jaws, turn the screw until the handles are almost closed, then squeeze them together to lock shut. They can also be used as temporary clamps in case a free hand is needed elsewhere.

There are a few specialized pliers in most workshops:

Long-nosed pliers can reach tight spots that others can't.

Flat-nosed pliers, have an end that is flat and square on the the end or nose, while on the combination pliers the end is rounded. A flat nose makes it possible to bend wire, or even a thin piece of sheet steel accurately along a straight edge.

  
Circlip pliers have metal pins that fit in holes in a circlip. Squeezing the pliers compresses the circlip and fits it in its groove. There's also a special pair of external circlips (right) that are sprung to push them open.

This type of cutters are called Nippers, or pincer pliers. They have a cutting edge at right angles to their length. They are designed to get a grip on and cut through anything sticking out from a surface. Rolling them on the curve of the jaws gives leverage too.

Side cutters work with any length, on things like wire or a steel pins. They're the most common cutters in the toolbox but they shouldn’t be used on hard or heavy gauge materials.

Bolt cutters cut heavy wire, rods, and bolts. Their compound joints and long handles give the leverage and cutting pressure that’s needed for heavy gauge materials.

Tin snips are the nearest thing in the toolbox to a pair of scissors. They can cut thin sheet metal, and lighter versions make it easy to follow the outline of gaskets. Most snips come with straight blades but if there’s an unusual shape to cut there is a pair with left or right hand curved blades.

Aviation snips are designed to cut soft metals. They’re easy to use because the handles are spring loaded open and double pivoted for extra leverage.