Meditation
Meditation is the state achieved from intense concentration on a single object until all other thoughts vanish and all that is left is an intense awareness of the object and nothing else is there in mind for some time.
Meditation is one of the Eight branches of yoga classified in Patanjali's Yoga Sutras. Called dhyana, meditation is considered the highest practice and is the final step before ultimate hapiness.

Meditation definition:
"meditation means sense withdrawl (pratyahara) and concentration (dharana), sustained into contemplation (dhyana), with the aim of triggering a super-conscious state (samadhi), which is one of intuitive realization of the identity of the individual soul or spirit and the cosmic soul or spirit."

Benefits of meditation:
Meditation helps reduce stress and anxiety, maintains blood pressure at normal levels, and improves concentrating abilities, clarity and improves creativity. - meditation calms the fluctuations of the mind.
A simple way to do meditation:

First, sit in a comfortable position, either on a chair or on the floor, with your back and head in a staright position parallel to each other in a straight line.
Take a couple of deep breaths, which are called ujjayi pranayama or nadi shodhana.
Close your eyes.
Breathe easy through your nose.
Focus on your breath - cool air in, warm air out. If the mind wanders about and it feels difficult to concentrate, gently bring it back to the breath.
That's it. Start with a 5-10 minute meditation and work your way up to 15, 20, 30 minutes or more. The more you meditate properly, the more benefit you will reap.
A variation that may make things a little easier at the beginning is to count your breaths.
According to Swami Vishnu Devananda, meditation is "a continuous flow of perception or thought, just like the flow of water in a river."

Principles of Meditation
The basic principles of Meditation are:
Have a good and quite place and a specific time for meditation. Try doing it daily in a routine.
Try to choose a time when your mind is not occupied by worldy thoughts and worries.
Sit up straight with your back, neck and head in one line, parallel to each other facing north or east.
Condition your mind such so as to remain quiet for the duration of your meditation session.
Regulate your breathing. Start with 5 minutes of deep breathing. Then gradually slow it down.
Follow a rhythmic breathing pattern - inhale and exhale.
Initially let your mind wander. It grows more restless if you force to concentrate.
Then slowly bring it to rest on the focal point of your choice.
Hold your object of concentration at this focal point throughout your session.
Meditation happens when you reach a state of pure thought. Even while retaining an awareness of duel self.
If you follow these steps diligently you will soon be able to attain a super-conscious state.