I am often asked advice on the practice of meditation. One of the most helpful guides I have found for meditation is in the Tibetan Book of Living and Dying, by Sogyal Rinpoche, ISBN 0-7126-1569-5.

Chpt. Bringing the Mind Home, Pg. The Mind in Meditation: ...There is a famous saying: "If the mind is not contrived, it is spontaneously blissful, just as water, when not agitated, is by nature transparent and clear." I often compare the mind in meditation to a jar of muddy water: The more we leave the water without interfering or stirring it, the more the particles of dirt will sink to the bottom, letting the natural clarity of the water shine through. The very nature of the mind is such that if you only leave it in its unaltered and natural state, it will find its true nature, which is bliss and clarity. So take care not to impose anything on the mind or to tax it. When you meditate there should be no effort to control and no attempt to be peaceful. Don't be overly solemn or feel that you are taking part in some special ritual; let go even of the idea that you are meditating. Let your body remain as it is, and your breath as you find it. Think of yourself as the sky, holding the whole universe.

Pg. Calm Abiding and Clear Seeing:  The discipline of the practice of Calm Abiding is to keep bringing your mind back to the object of meditation, for example, the breath. If you're distracted, then suddenly, the instant you remember, you simply bring your mind back to your breathing. Nothing else is necessary. Even to ask, "How on earth did I get so distracted?" is just another distraction. The simplicity of mindfulness, of continuously bringing your mind back to the breath, gradually calms it down. Gradually, mind will settle, in the mind.

As you perfect the practice of Calm Abiding and you become one with the breath, after a while even the breath itself as the focus of your practice dissolves, and you find yourself resting in nowness. This is one-pointedness that is the fruition and the goal of shamatha, or Calm Abiding...

Pg. Thoughts and Emotions: The Waves and the Ocean: When people begin to meditate, they often say that their thoughts are running riot and have become wilder that ever before, But I reassure them that this is a good sign. Far from meaning that your thoughts have become wilder, it shows that you have become quieter, and you are finally aware of just how noisy thoughts have always been. Don't be disheartened or give up. Whatever arises, just keep being present, keep returning to the breath, even in the midst of all the confusion...

If you wish to develop your mediation practice, the general advice is to practice regularly. Try to choose the same time each day, in a place you feel relaxed, sitting comfortably (but preferably not on a bed where there is always a tendency to relax too far!). Perhaps try 10mins at first and increase up to 30mins. You can focus the mind on your breath or on a positive image/object such as a candle flame, crystal or spiritual icon of your choice. Whatever you choose, try to keep it consistent so that the mind isn't distracted. Above all, be patient!