Sit down quietly for a few minutes and focus on your breath. While you do this, close your eyes and focus on either a pleasant, or an unpleasant sensation. For example, you might feel some pain in your legs from walking all day, or some back pain caused by sitting down with bad posture. Or maybe you're feeling very relaxed.
If you are focussing on a pleasant feeling, imagine you were giving it away to the people you care about. For example, to your friends and family.
And conversely, if you are focussing on an unpleasant sensation, pretend as if you are taking the burden on behalf of someone else you care about, so they don't have to feel that sensation.
We try very hard to hold on to pleasant feelings and sensations and to get rid of unpleasant ones. This creates tension and resistance in the mind. By imagining that you're sharing these pleasant feelings, or taking on unpleasant feelings so that others don't have to, you lose some of that built up tension in your mind.
I found that this meditation leads you to think positive thoughts about the people you are taking the pain from or passing the pleasant sensation to, which is an added bonus.
Source: The Headspace Guide to Meditation