How to Awaken Love and Compassion

1. Loving Kindness: Unsealing the Spring

When we believe that we don't have enough love in us, there is a method for discovering and invoking it. Go back in your mind and recreate, almost visualize, a love that someone gave you that really moved you, perhaps in your childhood. Traditionally you are taught to think of your mother and her lifelong devotion to you, but if you find that problematic, you could think of your grandmother or grandfather, or anyone who had been deeply kind to you in your life. Remember a particular instance when they really showed you love, and you felt their love vividly.
Now let that feeling arise again in your heart, and infuse you with gratitude. As you do so, your love will go out naturally to that person who evoked it. You will remember then that even though you may not always feel that you have been loved enough, you were loved genuinely once. Knowing that now will make you feel again that you are, as that person made you feel then, worthy of love and really lovable.
Let your heart open now, and let love flow from it; then extend this love to all beings. Begin with those who are closest to you, then extend your love to friends and to acquaintances, then to neighbors, to strangers, then even to those whom you don't like or have difficulties with, even those whom you might consider as your "enemies," and finally to the whole universe. Let this love become more and more boundless. Equanimity is one of the four essential facets, with loving kindness, compassion, and joy, of what the teachings say form the entire aspiration of compassion. The all-inclusive, unbiased view of equanimity is really the starting point and the basis of the path of compassion.
You will find that this practice unseals a spring of love, and by that unsealing in you of your own loving kindness, you will find that it will inspire the birth of compassion. For as Maitreya said in one of the teachings he gave Asanga: "The water of compassion courses through the canal of loving kindness."

Tonglen Practice
from The Tibetan Book of Living and Dying by Sogyal Rinpoche

I read this ages ago in the book The Tibetan Book of Living and Dying, and I found it on this webpage, along with some other methods for invoking compassion. This practice is called 'the Metta Bhavna" or Metta practice. Its a standard in Buddhist teaching but I LOVE the way Sogyal Rinpoche describes it in this passage.