This is general zen meditation as I understand it
Sit on a firm surface like a thinly carpeted floor. Put the outside of your right foot on top of the inside of your left thigh. Then put your left foot across the top of your right shin and rest your foot on the inside of your right thigh. This is called the lotus. You can also reverse your legs. I do half of my meditation with my right leg on the inside and half with my left leg on the inside.
If you can't get into this (it took me about 6 years..), you can do a half lotus to gain flexibility.
Follow the same directions with your right leg. With your left leg, tuck it under your right leg so that it lies on the floor.
There are a variety of hand positions. My favorites are cupping my hands on top of each other in my lap or putting my hands palms down or palms up on my knees.
Do an image search on google for "lotus position" to get a visual.
Once your in the lotus or half lotus (or simply cross legged if you can't get into the half louts), let your back fall into alignment. Visualise the bottom of your spine growing out of the floor like a tree. Your head should naturally sit on top of your spine. This will fix your gaze forward and slightly down.
I like to breath in and out of my nose because one's nose hairs act as a filter for the air (exhaling through the nose blows the debris back out into the environment).
Now, don't think about anything
Over time, you will find that their are two types of thoughts. Uncontrollable ones and controllable ones. The trick is to listen to the uncontrollable thoughts with out conciously responding to them. When a thought enters your head, don't try to push it out. don't try to rationalize it or analyze it. Just let it run around unchecked untill it decides to leave on its own accord. These thoughts are often refered to as the "monkey mind". Sit like this untill you get sick of it.
Here are some helpful tips.
Pain is good. It drowns out all of your other thoughts and gives you a definitive thing not to think about.
Don't worry about not getting it. It takes practice.
Practice all of the time. When someone is talking to you, listen to them instead of yourself. When your sitting around, try to zen. The more you try, the better you'll get at it.
Want enlightenment with out ever expecting to recieve it.
hope this helps and jah bless