Meditation has many definitions. For me, it is a process that isolates my mind from external distractions wherein I can explore thought and memory in pure abstract; a place where my conscious mind directly observes the swirling undercurrents of the subconscious. In physiological terms, it is the conscious lowering of brain wave frequencies to levels normally associated with sleep. While one could certainly raise his brain wave frequencies using similar techniques, the ensuing mania would not be characteristic of traditional meditation.
Possibly the easiest method to attain a meditative trance state is through entrainment. Basically, if you put two oscillating systems in contact with one another, their frequencies will synchronize. In practice with regards to meditation, this is achieved through the introduction of subaural beat frequencies generated by competing audible tones. The beat frequency remains static at the target frequency and if perceived long enough without other sensory input, the brain's frequency starts to synchronize with the desired frequency. The same effect can be achieved with any other repetitive sensation, e.g. strobe lights, vibrators, and spoken mantras.
Entrainment is a great way to get started with meditation as it requires virtually no discipline. All you need is a pair of headphones, a CD player, and some brainwave music. Of course, you don't have to get the hippy new-age albums featuring Ocean Sounds, Birds Chirping, and Wind Chimes, but they're less boring than straight tonal white noise. The advantage of the latter being you can make your own fairly easily. However, I find it's a lot harder to "come back" when the music lacks real-world context, as I discovered after spending four hours under my Mother's desk in her home office after slapping together something in RealPlayer and foolishly putting it on loop.
The main problem with entrainment is lack of control. Since the meditative focus is coming from without, you can't change it once you're under. It follows that one should move the focus within if you're going to get serious with it. The other advantage of using internal focus is that it's always with you. Bored, stuck in a meeting? Slip away into your own mind while the boss' words cease being stupid and become comical as you stare out of the glassy windows you call eyes beyond the vast plains of your imagination.
Sorry, got away from myself. I'll get more coffee.
That's better. As I was saying, while internal focus is superior, it is also more difficult. Much more difficult. I recommend experimenting with entrainment for a while before moving on, so you can get a feel for things. Not to totally dissuade you from this technique, I should add that in mastering this form, you learn a lot of stress management as well that you will apply in everyday situations. You know that eerie calm you see in Buddhist monks and the like? Well, they weren't born that way.
It wasn't until college that I finally learned how to properly meditate. I had tried focused breathing and all that crap in high school with poor results and decided that tapes were good enough. This was back in the halcyon days of '01. I was living on my own for the first time in my life; the nation was gripped by terror after watching the collapse of the twin towers; and I had recently discovered what would become two of my greatest loves: k5 and the Europe@n Grind (RIP). As coffeeshops go, this was teh best evar. People sat down and actually talked with one another in relatively civil fashion. Among the regulars was a sports hypnotherapist (I don't know either) and a neo-pagan shaman.
The three of us would often get into discussion regarding the vagaries of the human mind. After we quickly realized the sports therapist was mainly there to pick up women half his age, the shaman and I kept the discussion between ourselves. After many an hour chatting, he offered to show me how he meditated. We drove the short distance to his apartment and the lesson began.
I highly recommend having someone with you as a guide the first time. Yes, it's an external focus, but it's kind of like having training wheels while learning to ride. You get the gist of it while not worrying about falling down. Anyway, the first thing to do is get comfortable. None of this awkward Lotus position crap. That'll just mess up your joints. Lay down. Or sit. Or whatever's comfortable for you. Remember, whatever position you're in when you go under, that's the position you will remain in for a long time. Speaking of which, make sure to set aside at least an hour to meditate, especially beginning; it can take a long time just getting comfortable.
Once you're in position, work out any kinks you may have. Pay special attention to blood flow and make sure nothing's restricted. Rub your eyes and clear your throat. If you don't, these things will bother you later. Now close your eyes - not tightly, let them stay shut on their own. Stay relaxed in your breathing. I'm sure you've heard of the efficacy of deep breathing for relaxation, but it fails it for meditation. Increased oxygenation will put you to sleep, not to mention give you something to needlessly worry about. Try to forget about your breathing and let the autonomic parts of your brain handle it.
Now we focus. The following instructions apply equally for yourself or your guide should you choose to use one. Establish a scene in your mind's eye, something calm. The imagery should also transition to a metaphor for the annhilation of your body. I know that sounds weird, but it'll make sense as we move on. The aforementioned shaman used a road of light leading to a door amidst a field of night. That was a little too astral for me and I've since adopted the Hawaiian rainforest for my backdrop. Take time to examine the details. Ask questions like "what is the door made of?" or "what's the weather like in Oahu this time of year?" This will help cement the image in your mind.
Next, focus on relaxing every muscle in your body, starting with your face and ending in your soles. Make sure to get everything. Don't worry about having to backtrack either. I usually have to redo my cheeks a couple of times. This is a good time to incorporate annhilating imagery, such as "illuminating light" or, in my case, black ooze dripping out the tension. During the relaxation phase, slowly count from one to ten. Counting gives your conscious mind something to focus on so it doesn't get distracted. If you think you're going to fast, just slow down. Also, the head and shoulders generally take longer so don't freak out if you're up to seven by the time you get to your waist. Do not, however, go back in the count; you'll only get confused.
Feeling relaxed? Good. Now let's get rid of that pesky corpse. Here imagery is key. The common theme is warm, white light, but I prefer the Lake of the Black Waters (remember that ooze? It collects). This process is a reverse of the previous one. Take a step into the Lake. The water's warm, inviting, and dissolving. Replace the sensation of your feet with the image. Move up your legs, and don't forget to count backwards from ten. You don't want to be thinking about the office when you're hip deep in Nothing. Once you're up to your neck, dive in! Or open the door. Or whatever floats your boat.
If all goes well, you shouldn't feel a thing nor have any awareness of your surroundings. If part of you or your environment still lingers, dive down deeper. In such instances I like to think of the Waters invading my lungs, dissolving them, moving onto my bloodstream and then straight for the brain.
What you do now is your business.