All the meditation techniques can be grouped into two basic approaches:

Concentrative Meditation
Mindfulness Meditation.

Breath:
The simplest form of concentrative meditation is to sit quietly and focus the attention on the breath. Ones breath is correlated to ones state of mind. When one is anxious, frightened, agitated, or distracted, the breath will be shallow, rapid, and uneven. But when the mind is calm, focused, and composed, the breath will tend to be slow, deep, and regular.

Image:
One simply focuses his attention upon a single physical object such as a candle flame, fire in a fireplace, a tree or flower, artistic items such as religious allegories and illustrations, water (either a bowl of water, a gently flowing fountain, ocean, or beach)

Visualization, look at the way the candle changes colors, a flower how beautiful it looks, meditate it as a bud opening out.

Mantra/ mantrum is one or more words or syllables, from the Vedas - like the mystical word 'OM', or your favorite verse from The Bible, The Koran or any other verses you like which are repeated often chanted aloud meant to vibrate. Restating this phrase creates a sort of hum in the ears, a sense of vibration in the abdomen, chest, and throat, which is very comforting and helps to still and focus the mind.

Emotion:
Looking at a picture of something or someone you love, respect. Memorable moments you have spent with them green gardens, flower beds etc.

Visualization:
Thinking of your favorite god or goddess, feeling their face and looking into their eyes and thinking of all the wonders and miracles done by them.

Music:
Peaceful and melodic music can help focus the mind on the practice of meditation. Sometimes it will be difficult to get rid of everyday thoughts, focusing on the gentle rhythms of a carefully chosen piece can be very useful in re-directing the mind.

To look deeply is to use mindfulness to see the true nature of things. Instead of narrowing your sight to a selected field as in concentrative meditation, here you will be aware of the entire field. This involves being aware of the continuously passing parade of sensations and feelings, images, thoughts, sounds, smells, and so forth without becoming involved in thinking about them. The person sits quietly and simply witnesses whatever goes through the mind, not reacting or becoming involved with thoughts, memories, worries, or images. This helps them to gain a more calm, clear, and non-reactive state of mind.

Simple put, meditation is nothing more than relaxed concentration. This concentration can be directed toward anything you wish: simple actions, your daily chores, can be eating (savoring every bite and drink), a deity (visualizing your favorite god), working, a goal or nothing at all! Keep track of where your feet and your hands are.

Meditation can bring about a healthy state of relaxation where the body gains a state of profound rest with deep relaxation.

During meditation, blood pressure stays at 'low levels' but fall markedly in persons starting meditation with abnormally high levels of heart rate, respiration rate, plasma cortisol (a major stress hormone), pulse rate, and increased EEG (electro encephalogram) alpha, a brain wave associated with relaxation, the same time, the brain and mind become more alert, indicating a state of restful alertness. One can feel the fall in metabolic rate within a few minutes of starting meditation.

Meditation reduces activity in the nervous system. During anxiety and tension the level of lactate in the blood rises when one meditates the blood lactate levels decrease four times faster than people who lay down to rest due to the faster circulation delivery of oxygen to the muscles.