In this form of meditation, which is called discursive meditation, the thinking process is not stopped but redirected and clarified; thoughts are not abolished but made into a vehicle for the deeper movement of consciousness. This is typically done by focusing the mind on a specific topic, and allowing it to follow out the implications of that topic through a chain of ideas, while at the same time keeping it focused on the topic without straying. By doing this, the meditator gradually transforms thinking from half-random mental chatter into a powerful and focused way of understanding; at the same time, the knowledge that comes out of meditation of this sort can have a good deal of value on its own terms.
The mind of the meditator thus focuses on a previously chosen image or idea, which is called the theme of the meditation. The meditator considers the theme and follows out its implications and consequences, restraining the mind whenever it tries to stray from the theme but giving it free rein to follow the theme as far as it can. Thus this form of meditation has two positive effects. Like every other form of meditation, it teaches mastery of attention and awareness. Unlike most other forms of meditation, it enables the meditator to understand the themes of meditation to a depth that ordinary thinking rarely reaches. Furthermore, many of the myths, symbols and teachings of the chosen tradition are specifically designed to yield up their meaning only to careful, focused attention.
Certain preliminaries are valuable. The most important is the selection of a theme. Every aspect of study and practice can provide themes; books worth studying are among the most common sources. Beginners often choose vast sprawling themes and either flounder about in them or skate over the surface, missing the potential depths of the practice. As a general rule, if your theme takes more than a fairly short sentence to describe, it's too large for a single meditation and should be broken up into smaller bits, then recombined later.
Start meditation practice by sitting down on a chair with a plain, cushionless seat. Sit far enough forward on it that your lower back isn't resting against the back of the chair. Your feet should be flat on the floor. Straighten your back without stiffening it, and hold your head upright, without letting it slump forward. Your hands rest palm down on your thighs, and your elbows are against your sides. This posture for meditation, unlike the cross-legged positions common in Eastern systems of meditation, doesn't seal your energies off from the rest of the cosmos. This is an important aspect of spiritual practice, we are always part of a larger world.
Most people find it useful to meditate in the same place each day, and at the same time of day (or the same point in the daily cycle for those who have variable schedules - right before breakfast, say). If possible, it's best to meditate facing east, to take advantage of currents in the subtle body of the Earth. A clock placed so that you can see it without moving your head completes the setting for meditation practice.
Once you've settled into your position, consciously relax each part of your body, starting with the top of your head and moving step by step to your feet. Then spend a few minutes paying conscious attention to your breath, breathing in and out slowly, evenly and fully. A traditional breathing exercise called the Fourfold Breath is commonly used here. Breathe slowly in while counting mentally from one to four; hold your breath in, while counting from one to four; breathe out, counting from one to four; and hold the breath out, with the lungs empty, while counting from one to four, and repeat. The counts should all be at the same pace, and the breath should be held in or out with the muscles of the chest and diaphragm, not by closing the throat, which can lead to health problems.
After you've paid attention to your breathing for perhaps five minutes, turn to the theme of the meditation. State the theme silently to yourself in a few words, or visualize it before you in a single image. Keep your mind focused on it for a time, and then start thinking about it, turning it over and over in your mind, exploring its implications and connections. Choose one of these that appeals to you, and follow it out as far as you can. When your thoughts veer from it, as they almost certainly will in the early stages of training, don't simply bring them back to the theme; follow your straying thoughts back to the point where they left the train of thought you were following, and proceed from there. Over time, this will teach your mind to return to your theme as readily as it strays from it.
It's important to set a period of time for the meditation in advance, and stick to that, even if you don't think you're making any progress at all. Five minutes of breathing and ten minutes of actual meditation makes a good length of practice session for beginners. When you're done, pay attention to your breathing or practice the Fourfold Breath again for a minute or so to help yourself make the transition back to ordinary awareness.