Macro Photography for Beginners: Extension Tubes.

A very common way to get into macro work is to employ extension tubes or extension rings, the name varies a bit. These are, in the simplest form, just a set of varying size bayonet socket/plug combinations that are inserted between the lens and the body. Usually they are available in a set like 12mm, 20mm, 35mm. These measurements are the amount by which each tube will push the lens out from the body. They have no optical component so don`t distort the image at all. They can be stacked by plugging one into the next so that, for example, the above rings would provide a total maximum extension for the lens of 67mm.
The simplest types make you lose all contact with the lens so that auto focus and aperture readout and control are lost, therefore the camera has to be in aperture priority for ambient light and manual mode for TTL flash and you have to remember to focus manually with aperture wide open and then set the aperture down before shooting. More expensive tubes will provide electrical and mechanical control of the lens to make life easier. Often there are independent manufacturers of these tubes (Kenko for example) so you are not always tied into buying expensive brand name parts.

Prime lenses like 35mm or 50mm focal length tend to work better than zooms but zooms make life convenient and easier to frame the subject.

Realise though that most lenses are not designed for close-up work so when they are extended like this they are not giving their optimum performance. Maybe try tubes plus reversing the lens to improve the situation.

In my case I have the Nikon reversing ring BR-2A and the adapter BR-3 to hold filters on the bayonet end of the lens. These two can be screwed together and used as a short extension tube. Once you get all these odd bits you tend to find new ways to use them.

Upside. Relatively cheap, they don`t introduce optical distortions.
Downside. Fiddly and may need to uncouple or recouple a tube or two a few times to get the image you desire.