The Buddhist tradition of mindful breathing trains the body and awakens the spirit. This practice works extremely well; I use the basic technique in prayer ("Breathing in, Let God." "Breathing out, Let Go.", etc.).
Basically, it is attention upon the breath (through the nose), combined with the mental recitation of the given mantras. The stronger you "speak" them in your mind, the better. You may however benefit from not placing too much energy upon them. You will quickly find what works for you. The important part is to sit and truly do this, as it works, and reveals a few major surprises about the body, mind, and spirit.
Inhaling with attention upon the breath through the nose, recite in your mind "I am breathing in long." Exhaling, "I am breathing out long."
Moving further, "Breathing in, I am tranquillising mental activities."
You will find that the body truly responds to these ideas. Note that the experience of bliss is among them; you may command yourself into experiencing bliss.
These sixteen commands combined are extremely powerful.
First Tetrad, Contemplation of the body
1. Breathing long
2. Breathing short
3. Experiencing the whole body (of breath)
4. Tranquillising the bodily activities
Second Tetrad, Contemplation of feelings
5. Experiencing rapture
6. Experiencing bliss
7. Experiencing mental activities
8. Tranquillising mental activities
Third Tetrad, Contemplation of the mind
9. Experiencing the mind
10. Gladdening the mind
11. Centering the mind in samadhi
12. Releasing the mind
Fourth Tetrad, Contemplation of Dhammas
13. Contemplating impermanence
14. Contemplating fading of lust
15. Contemplating cessation
16. Contemplating surrender (or relinquishment)
For further reference and explanations of the practice, see:
"True Love" by thich nhat hanh
"The Path of Emancipation" by thich nhat hanh
The very end of "The Path of Emancipation" contains a slightly modernized version of the steps.