This technique is credited to Nicole Jeffries.
Think of a person you want to love. It could be someone you already love, or it could be someone you feel neutral toward. It could also be someone you don't like! Sharing loving kindness has many mental health benefits, and has been taught by many spiritual teachers, including Thich Nhat Hanh.
In your mind's eye, imagine, experience or pretend there is a ribbon that forms a figure 8 between your heart, and their heart. Send that love out and experience it grow and grow as it goes back and forth between you.
Sharing love is one of the most immediate ways to experience love. In loving people that are hard to love, we also learn to love the more difficult parts of ourselves.