Choosing yours
More than any other tool, a ratchet can last you a lifetime. Quality ratchets can be serviced inexpensively and so should never degrade. Sockets are interchangeable because they are all standard. Buy the ideal ratchet you can afford, even if you get inexpensive sockets to get started on with.

Socket release
Sockets will be held onto the ratchet utilizing a small spring-loaded ball on the side of the square travel. After applying a whole lot of drive, I've frequently found sockets get stuck on the drive and the only way to get them off is to hammer the ratchet on to the floor or even grip it in a vice. Top quality ratchets include a button on the trunk which smoothly pushes off the socket when you are ready to release it.

1/4 in . - Used for smaller sockets and precision work. Valuable for dismantling individual pieces on the bench.
3/8 inch - The middle sized, and for me, most readily useful size for standard use on a car. A 3/8" travel can drive sockets of all sizes. It is big enough to use quite a lot of force, but not too big to match into tight spaces
1/2 inch - 1/2" sockets are generally employed for nuts and bolts from around 10mm or more. A 1/2" travel socket can apply enough drive to undo all nuts on a car.
There are also 3/4" and 1" ratchets but these are being used on trucks, tanks and industrial machinery.
Tooth count
Inside a ratchet there exists a toothed wheel which lets it freely rotate as you tighten the nut. Each simply click you hear is a tooth passing the ratchet. The more teeth there are, the a smaller amount movement is necessary on the come back stroke. A ratchet with 75 teeth will work considerably faster when compared to a 32-tooth ratchet. Making large tooth-counts requires quality engineering and developing, so as an over-all guide the Ratchets Wheel better top quality tools will have a higher tooth count.

Drive sizes
socket-drive-sizes
All ratchets accept sockets by using a square travel and mostly there are 3 sizes of drive. Everywhere in the globe these sizes are given in inches - even though the sockets will be metric.