Macro shooting..

For the highest quality, a macro lens.

Other techniques are close up lenses (cheap and good when main lens stopped down), bellows, extension tubes - you need a good book on macro techniques.

Don't forget compact cameras though, such as the MX-1. The close up/macro modes on these can get very, very close and the results can be amazing.

There isn't a "best way".... just different

An old manual lens with aperture ring on a reversing adapter can be astonishingly good (50mm or 28mm). BUT the exposed element of the lens has to be incredibly close to the subject.

Extension tubes are helpful for making a good lens 'short-sighted'. For example, it's helpful to get a touch closer with the DA*50-135. Results are great, and not limited to macro (just getting a bit closer).

Extension tubes with a reversed lens gets silly... but fun to try.

Dedicated macro lenses are helpful for close detail, but taken further away (e.g. 180mm macro lens will get detail from further away).

Closest and cheapest option is a K-mount reversing ring, and a good prime (doesn't have to be Pentax )

Next option is extension tubes, but watch out for the various issues with stop-down-metering and electronic control pins on DA*/DA series lenses (search the forum here).

And there is always the Raynox type clip-on adapters that can give pleasant results. The cheaper devices tend to "bloom" at wide apertures and can have significant distortions. But they're easy to fit in the field.

Hope that helps!
Matt

As Matt says, there are lots of ways with Macro photography. A true macro lens is the easiest option, but I'm not sure if it produces the highest quality as John has said. I've experimented with all manner of different lenses and techniques and the highest quality results have been obtained by using a butchered FA 28-80 zoom lens (all glass removed, but aperture still working) and a Nikkor EL 50mm F2.8 enlarging lens reversed onto the front of the FA zoom. That's all getting a bit technical, but it produces results that are (a) a lot higher magnification) and (b) better quality than a macro lens can achieve.

Macro lenses also vary tremendously, the Pentax 100mm F2.8 variants are a good bet. Finally, the cheapest option, i.e. extension tubes and a 50mm prime can also produce stunning results and this would be my recommended starting point. If you find you like it and get on with macro photography, it's worth moving on to try some of the other techniques.

Don't forget also that good lighting is the most critical aspect of successful macro photography, this means you will need a diffused source of light, e.g. a flashgun with some sort of diffuser attached. My best results have been with a manual flashgun and a home-made softbox that fits over the flash head.

Regards
David

One other option not mentioned yet is simply stacking lenses reverse a lens in-front of another (longer) lens. Magnification is the the focal length of the (longer) lens /focal length of the reversed lenses.
Ideally done with a coupling ring but can be done just by holding the reversed lens in place.

If you have more than one lens you can try it for nothing!

Some combinations give vignetting or excessive magnification making it effectively useless, but a 50mm prime with the kit lens (zoomed in) gives ~1:1 simply.