Zen Center of Georgia
Meditation is a form of unfocused concentration. Zazen is seated meditation.
Unfocused is not entirely accurate. The focus tends to be difficult, things that force you to be present in the moment, each and every moment. The things chosen as the points of focus tend to be fairly boring - your breath, your posture, perhaps a mantra (a phrase repeated in your head with each breath), or perhaps focusing on having a clear mind. As simple as these are to do for a short period, keeping it up is quite difficult when you first start.
The first few times you try to meditate, you will find your mind jumps to something else fairly quickly. The human mind always shifts attention to what it considers most important at that point in time. The shift is not under conscious control, hence the difficulting in learning to meditate well.
Continuied, diligent practice will train your mind that remaining with your point of focus is important. This can take years and if you quit practicing for a while it's a skill which will fade the same as musical skill will fade without practice.
When you first start meditating, it's important to pick a time of day and a quiet spot to practice, a spot and time with few expected distractions. With no one to persuade you to meditate and it's easy to blow it off. Once you've done it once, it's easier to miss it the next day, until you find you are no longer meditating.
Try to meditate for the full time you aim to each day, but if your schedule is busy, meditate for at least 5 minutes. If you can't find 5 minutes, then it's an excuse your giving yourself not to sit.
Try to relax and give yourself a few clearing breathes as you start. This will help set the stage for settling into meditation. Some people visualize a progressive relaxation of their body in stage: legs; torso; hands; arms; then head.
The how to of meditation
There are many ways to meditate. The one described here is common to Rinzai Zen Training.
Get a comfortable cushion that will elevate your bottom a few inches off the ground. Sit on the edge of the cushion, so your pelvis tilts forward with your legs crossed. For a while you will want to avoid having your legs resting on one another. This could become uncomfortable in a prolonged sit. More advanced postures include full lotus, half lotus, and Burmese lotus. Feel free to try these out to see if they work for you. Sit erect, head erect, and shoulders back. This will allow for comfortable breathing without collapsing the body over the solar plexis. There should be a bit of a curve in the lower back, a slight arching, that helps push your chest out slightly and give good posture to your seated position. Your head should be facing directly across from you. The head being erect should feel almost as if there's a thread holding your head up straight. Make a fist with one hand and wrap your other hand under, slightly around it, cradling them in your lap, your arms forming a circle against the front of your body.
Once you have your body positioned properly, try to look at your entire environment, taking it in all at once without focusing on anything specific. It will be like the entire scene is peripheral vision. Aim your eyes about four feet in front of you without looking at anything in particular. If you find this difficult, pick two objects at opposite extremes of your vision and try to maintain a visual awareness of them without turning your eyes to seen them. I've heard this process described as starring into infinity.
You should try to do the same type of thing with all your senses, being aware of everything without focusing on anything. For hearing, I like to pick two moderately consistent sounds and just be aware of them at the same time. Once your senses are set, concentrate on your breathing and posture. With each breath, give it a count, slowly, in your mind's voice, drawing the mental sound out for the entire extent of the exhale. Inhale, and repeat. Once you've reached a count of ten, start back at one. If you find your mind has wandered, and you will, just bring your mind back to one.
Your mind will wander. This is natural. It's also what your training your mind not to do. Don't get upset about it. Think of your mind as a little puppy you're training. You don't get upset at puppies, you just scoot them back onto the newpaper. Treat your mind with the same compassion.
It's best to use some form of timing that doesn't make noise during the sit. That should cut down on the distraction factor.
Meditating on ones own is the core of a meditation practice, but it works better when supported by periodic practice with a group. Once you have a good practice with a group, it's also advisable to find a teacher to train under. They can help avoid certain pitfalls common to training.