While there are ways to engage in macro photography without buying a true macro lens, in this article we look at how to choose macro lenses.
Unless you have a really big budget, it is important to define the type of macro photography you intend to engage in.
This will help you determine the focal length you will need thus streamlining the selection process.
Briefly, here are the various uses for different macro lens focal length:

1. 50-60mm is generally used for product photos and smaller objects
2. 90-105mm is the range of choice for flowers, insects and other small animals and objects
3. 150-200mm range allows the photographer to stay further away from the subject.
   Recommended for animals that are too sensitive or too dangerous to approach.
   

From the above, its obvious that a serious macro photographer will eventually have at least one of each.
However, given the prohibitive price of true macros, it is imperative to make an honest assessment and see which area you are likely to concentrate on.
Keep in mind that a true macro lens should be technically capable of reproducing the subject on at least a 1:1 ratio.
This means that the image of the object on the sensor or the film should be AT LEAST actual size.
Anything less than a 1:1 ratio is the mark of a mere macro / close up setting and not a true macro.
This sort of information should be indicated on the lens and / or the owners manual.
Lastly, before buying the lens, make sure that you read as many reviews as you can about your choices.
After all, these lenses are not only priced prohibitively but they are also likely to be a not so common expense item.
What this means is that a wrong choice of lens may leave you with an undesirable lens that will be hard to sell without taking on a big loss.
So take your time and choose wisely.