The suggestions above are pretty good overall.
If you're cleaning up an old pipe, ream back the cake, but you may want to avoid going all the way back to the wood on a really old pipe, lest you reveal the carnage that lies underneath, and is protected by, the existing cake.
I use a variety of tools, depending on the needs of the reaming job. I'll use a Pipnet, a Buttner-- especially on conical chambers -- any of several Swedish stainless steel reaming blades, and/or glass paper wrapped around the end of a Pilot marker and affixed with rubber bands. The sandpaper is great for careful work.
I've used the S/A method, cotton ball method, and retorts, especially for really stubborn deposits in the airway. With a really stubborn ghost you may have to repeat the S/A or cotton ball method, or send the pipes out to Walker Briars for an ozone treatment.
Go slowly and patiently. Avoid ringing a bell that can't be unrung.
For regular maintenance, wiping down the chamber walls with a wadded paper towel or three gets a lot of gunk, and bristle pipe cleaners -- doubled over -- rubbed over the chamber walls clean up a lot of gunk.
Make sure that the mortise is spotless.
Use alcohol on Vulcanite stems and water with unscented detergent on acrylic stems. Don't use alcohol on acrylic stems.