This is a very good question, and I agree with everything said above. But let me give you my perspective which is that of grower with thousands of trees and not enough time to diddle with anything that won't result in a positive response.
I have two basic rules on how to begin styling that are so general that they encompass just about all bonsai. These are the first questions I ask, and if the answer to either is yes, then I begin the process, otherwise, I am inclined to just let things grow.
The first question is: Does this tree show me anything that would have bonsai potential? This is a very broad question, but it is really where you begin. An untrained tree may have several characteristics that would lend themselves to a believable bonsai, but I look for its strongest quality. For example, a completely untrained tree may have a fantastic nebari, but nothing else of a bonsai nature. If I see this, then I start the process of building a tree from the nebari. Usually this will mean a short tree with a thick trunk, but not necessarily. So the question now is, what do I do to build a trunk like that? This question will lead a whole chain of decisions that will build a tentative tree.
Of course, you need to know not only basic information about styling (rules!), but a good grasp of the qualities that actually make up a believable bonsai. Most beginners won't have this (naturally), and thus will feel lost. This is a part of paying your dues. You need to read, study, and especially work with other practitioners to learn this. We have a local study group, which is a small group of experienced folks who do nothing but sit around together for 6 hours about six or eight times a year and design or modify their trees. This kind of exposure is invaluable. General club attendance can also give you a lot of this, but on a less concentrated basis.
The other question is: What, if anything, is going wrong with this tree from a bonsai perspective. A completely untrained tree may not be showing much of anything in the way of a good bonsai characteristic, but it may be showing, or beginning to show an undesirable quality (fault). If this is happening, you need to take action to correct the fault before it gets worse. This could be something as simple as a whorl of branches on a pine that are beginning to create a bulge. You may not see anything usable at this point, but if you don't make the correction, any later potential may be lost or diminished by the fault. A VERY common beginner mistake is not to correct the rooting or nebari on a pine. Surface root correction is something that must be done every time a tree is transplaned (repotted). If left for more than a few years, a bad rootage will be uncorrectable. So, no matter how much time and energy you put into the tree past this point, it will still have a fault that diminishes its potential. A few minutes spent doing this root work every year or two would transform something atrocious into a believable bonsai (assuming you do other things correctly. I can't tell you how times I have seen pine trees with years, maybe even decades of work with roots that I can't even stand to look at.
Of course, once you have analyzed your trees, you either take the next step or leave them alone. But taking the next step requires another complete level of discourse, and assumes you KNOW how to either enhance its bonsai nature or eliminate the fault. This dilemma keeps drawing me into bonsai. The marriage of horticulture and art is a seemingly bottomless pit of potential possibilities. There is so much to learn, but the more you learn, the better your bonsai, and the deeper the passion.
Brent
EvergreenGardenworks.com
