There are several good lens options for macro photography. You could use extension tubes combined with a normal lens, which gives you some magnification. Or even better, you could reverse a normal lens, which combined with extension tubes gives even more magnification. The most convenient and flexible option though, especially for a beginner within macro photography, is to get a dedicated macro lens.
The most popular models come in focal lengths between 90-105 mm, and have 1:1 magnification. There are also shorter focal lengths such as 50 or 60 mm, but these have shorter working distances, which means you have to get very close to your subject, risking to scare it away. 1:1 magnification means that when you focus as closely as possible, your subject is as big on the sensor as it is in real life. So if you have a full frame sensor of 36x24 mm, it means that any insect you want to shoot that is 36 mm long, just about fits in your picture.
If you use an APS-C or Micro Four Thirds camera, you will get your subject magnified even more at 1x, as the sensor is smaller. These normal, 1:1 macro lenses, are made by most major brands, such as Sigma's 105mm, Canon's 100 mm, Nikon's 105mm, Samyang's 100mm, Tamron's legendary 90mm, Sony's 90mm and Tokina's 100mm. They cost around $400-$1000, and they are all sharp and great value for money.
Many these lenses have image stabilization, which is a good thing, as it makes composition a lot easier. Have a look at reviews and buy one that you like. You can't go wrong with a ~100mm 1:1 macro lens – image quality wise, most of them produce comparable results.
2. Location and weather
Some of the most interesting subjects to photograph with a macro lens are small bugs and insects. Flowers and various plants are also fun, and can often make interesting abstract images. The locations that offer the most to a macro photographer, is in my experience places with lots of flowers and plants. Botanical gardens are great.
The best time to go out if you want to shoot bugs and insects is whenever the outside temperature is about 17°C (63°F) or warmer, as insects tend to be more active when it is warm outside. On the other hand, if you are good at finding insects where they rest (I have personally found this very hard), they are more still when it is cold. Some macro photographers like to go out in early summer mornings to catch the insects when they sleep.
Overcast weather is usually better than sunny weather, as it gives a softer light.
If you are shooting very small subjecs, such as insects, the focal plane will be extremely narrow – a couple of millimeters or so. Thus, you will have to set your aperture to at least F16 to have a chance of having most of an insect in focus. With a small aperture like that, and the need for a high shutter speed, due to the shaking of the lens and the subject, a flash is a must. You can use any flash for macro photography, in most cases even the built in pop-up flash of cheaper DSLRs work well. My personal favorite is the cheap, compact and lightweight Meike MK-300.
There are some macro photography situations in which a flash is not strictly needed. One situation is if you are okay with shooting at F2.8 or F4, and there is plenty of sunlight. This could be the case if you are not going all the way to 1:1 magnification, and thus can get a good depth of field with a large aperture (when you move away from your subject, the depth of field will increase). The upside with not using a flash, is that you get more natural looking photos with natural light. But if you are going to shoot insects up close, and want to have more than a small part of them in focus, you will have to use a flash.
If you are using a flash for your macro photography, I highly recommend using a diffusor as well. A diffusor is simply any white, translucent material you can find, which you can put between the flash and your subject.
The larger the light source, the smoother and softer the shadows in your photos become. This is why huge octaboxes are popular in portrait photography. And this is why you should use a diffusor in macro photography: It makes the size of the light from the flash much larger, and thus the light in your photos will look less harsh, and the colors will come out better.
In the beginning I used a normal white paper that I cut a hole in and stuck the lens through. It was a bit flimsy though, and would get crumpled during transport. My next diffusor was a filter for a vaacuum cleaner, that I also cut a hole through and put around the lens. This was a great diffusor as well. Currently I use a purpose made soft diffusor, which can conveniently be folded together when not in use.
5. Shutter speed
In macro photography, you will find that the small vibrations from your hands when holding the camera will be enough to make the whole picture jump around like crazy. Combine this with trying to photograph an insect sitting on a plant that is swaying in the wind, and you have a real challenge. See the video at the top of this article, to understand what I mean. A high shutter speed is therefore to recommend, especially for beginners. Begin with a shutter speed of 1/250 or faster.
However, the light duration from a speedlight is usually extremely short, and can alone freeze your subject, even combined with a slower shutter speed such as 1/100 s. The reason is that the flash will stand for the majority of the light in the photo, so even if you happen to shake your camera, it will be barely noticeable in the exposure. With a short focal length macro lens, you can take nice looking photos even at 1/40 s shutter speed. The benefit of using a slow shutter speed, is that you can avoid the black background that you otherwise often get in macro photos taken with a flash. Instead, you can get some color into your background, making the photo look better.
In summary: Start out with a fast shutter speed. When you have practiced a bit, try gradually lowering the shutter speed, combined with a flash.
First of all, you can forget about autofocus right away. Most macro lenses' autofocus is not fast enough to keep up with the jitters and shaking that comes with 1:1 magnification. It is helpful to just give up the thought of autofocus from the very beginning, and learn to focus manually instead.
Second of all, forget about tripods. Unless you are shooting something completely static, such as a product in a studio, tripods will be very impractical to use in macro photography. For shooting insects or flowers outside, you will be disappointed to spend time setting up the tripod, only to discover that the small vibrations of the flower in the wind makes the photo blurry anyway. Not to mention that any insect will have flown away during the first 10 seconds of your 1 minute tripod setup.
Over time I have developed the following method of focusing, which I think gives the best results: Hold the camera with both hands, and preferably anchor your elbows against your sides or legs, to give even more stability. Then turn your focusing ring to approximately the magnification you want to get. Then focus, not by touching the focusing ring, but by slowly rocking towards the subject, while trying to snap the photo exactly at the right moment. See the video for a visualization of this technique.
If you can get one out of 5 photos focused and sharp in the right place, you can consider that a good ratio. Expect to throw away a lot of photos when doing macro photography.
7. Focal plane
As already mentioned, a close focusing distance will mean an extremely narrow focal plane. You will find that the best macro photos come when you utilize the narrow focal plane in clever ways. Thus, try to find subjects that are flat, and put them in the focal plane. Examples are small, flat flowers, or butterflies photographed from the side, or beetles with fairly flat backs.
Another example of utilizing the narrow focal plane in a creative way, is to make an insect's head "stick out" of the blurry bokeh, to make an interesting and aesthetically pleasing effect.
A common newbie mistake is to conveniently snap the photo from where you stand, at a 45 degree angle towards the insect or flower. This will make your photo look like every other newbie macro photo out there – it will be boring.
Try to find uncommon angles, such as shooting the insect from the side, from the front, or from below. Make use of your flip out screen if you don't want to crawl on the ground. If the insect sits on a plant or a leaf, try pulling up that plant to hold it against the sky – it gives you an interesting angle and a more beautiful background.
Something I did a lot as a beginner in macro photography, was to always go for maximum magnification. I thought, "the bigger the insect in the frame, the cooler the photo." But the truth is that you can often find a more beautiful or interesting photo if you back off a little, and let the insect look just as small as it actually is, depicted in its surroundings.
10. Sharp objects
And lastly, never put sharp objects such as knives or drills against your expensive macro lens. Despite what some YouTubers seem to suggest in their thumbnails, also avoid cigarette lighters and toothpaste. Putting stuff like this against your lens is only useful for clickbait thumbnails on Youtube!