Most effective meditation techniques to develop empathy, love and compassion for others?

I feel like a very cold and sensual person. Easily attracted to sensual pleasure but very cold and numb when it comes to bonding with other human beings. I want to change, and therefore I want to make a meditation plan in order to develop empathy, love and compassion for other human beings, and possibly extend it to all sentient beings in general. However, I'm not sure about how to make such a meditation plan. Based on your experience / knowledge, which meditation techniques are most effective to develop these emotions?