This practice is adapted from the Vijana Bhairava, an ancient and very powerful Sanskrit meditation text.
Step by Step
Sitting quietly, begin to become aware of the part of you that is aware. Something in you knows that you're alive, that you're breathing, that you're thinking. It's subtle and hidden, but that witnessing part of you is the basis of everything you experience.
Next, think of a loved one. Bring to mind someone to whom you feel close and think to yourself, "With all of our differences of personality and history, we both share consciousness. At the most fundamental level, the level of awareness, we are one." If that seems too abstract, consider, "Like me, this person seeks happiness. This person too feels pain." The more you can identify yourself with awareness, and recognize the awareness in the other person, the more deeply you will feel kinship.
Now think of an acquaintance. Bring to mind someone about whom you feel neutral, and have the same recognition: that there is one consciousness in both of you.
Think of an enemy. Bring to mind someone you dislike, perhaps someone you regard as an enemy, or a public figure you hold in low esteem. Remind yourself, "Different as we may be, the same consciousness dwells in that person as in me. On the level of awareness, we are one."
Feel the energy. Expand this idea to include the physical world, and allow yourself to contemplate the fact that a single energy underlies everything in the universe. On the level of subatomic particles, everything you see and feel is part of one great energy soup. With that in mind, look around and say to yourself, "All that I see, all that I touch, all that I imagine, is made of one single conscious energy."
Hold that thought. Questions will come up—and they're worth exploring. However, there is great power in simply holding the thought, "All this is one consciousness," as a mantra, and then trying to see the world that way. See how the thought of oneness softens the edges of your judging mind. Find out whether it eases feelings of frustration, anxiety, and fear. Notice how it tends to bring up feelings of peace.
After you've practiced this contemplation a few times, try taking it into your world. Look at the angry driver in the lane next to you, or the sad woman on the bus, and think, "The same consciousness is in that person as in me." Or see the person on TV whose politics you disagree with and think, "The same consciousness is in that person as in me."
As these practices become part of your life, look for different ways to recognize that kinship of consciousness—be recognizing the light in the eyes of an animal, or the living sap in a tree. As you do, keep observing the effect it has on you. When you notice that you're feeling more connected or more open, honor those feelings. Know that you are experiencing some of the qualities of the enlightened state of being.