One of the things the heart is associated with is flow and movement and rhythm. Breathing in a kind of rhythm, doing meditation-movement exercises (like qigong/taichi), dancing in the zone, or even mindful walking, flowing with life, feeling carried, feeling the lightness of being - all these are heart opening.
Ever notice when you sigh how much lighter you feel, and that something seems to be released from the center of the chest?
When your heart is open your hands become warm (as in reiki). Sometimes your hands want to move by themselves. There is a huge heart meridian extending to the hands for giving and for receiving. When your heart is open you want to socialize. Your arms want to hug. Sometimes there is fire burning in your heart and it almost hurts but it doesn't.
Sometimes like Miss Hepburn said singing helps because the open heart wants to sing. It's an expressing chakra. It wants to express in the world. The heart is the center of the soul (the astral part of us). We feel lighter and happier when our emotions are more pure. Listen to the birds singing at dawn - their heart chakras are wide open.
The heart is what makes us religious - we want to congregate when we're in the heart and love each other. Of course there are spiritual paths for every chakra but this is the one that joins hands and praises. The heart is a social chakra. That's one of the reasons it feels so unburdening in the heart when we share with someone who is a good listener, but sincere prayer can do this too.
As young children we are naturally open hearted unless that is interrupted by some karmic event or circumstance. All of Nature is the heart in expression. Looking through the eyes of the heart is liberating, healing, rejuvenating.
The physical body rejoices in the happiness of the heart chakra. The vyana vayu spreads prana throughout the body, driving the blood to spread the oxygen around to all parts, every cell. When we send loving energies to our bodies, every cell becomes warm in response as its own little "heart" responds like a child to its parent.
I've learned that to understand what's bothering the heart I need to use my intellect and to keep the emotions from going AWOL I need the intellect - but to actually open the heart - to actually FEEL it - the intellect just gets in the way so now I'm rediscovering the joy of my emotions and my body (the "lower" part of me that isn't "lower" at all) ((and no chakra works in isolation either))..............
..........p.s. One last tip: try my joy thread below. There must be a smile in it somewhere. Reach into your soul and add to it!