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?
There are different ways of going about this goal. 

A problem with merely reciting the standard formula could be that it may feel like internally, you are actually experiencing the opposite intention. 

Not being satisfied with oneself, even feeling aversion towards oneself, is quite common, especially in many Western cultures, and to extend metta from that position can be very difficult. The same thing is true when there are people you do not actually like, or even feel strong aversion or hate towards.

Personally, I suspect just reciting, going against one's actual experienced intention in the present moment could be counter-productive. 

There are other methods to try.

You may first want to consider if there is anything or anyone that actually does bring up a sense of compassion and a wish for well-being inside of you. 

Ajahn Brahm provides various suggestions: perhaps babies? Perhaps kittens or puppies? Some other animal? Perhaps somebody who showed you love and care when you were a child - one of your parents, one of your grandparents, etc.

Whatever or whoeever it is, is not so important, with the caveat that somebody you have been sexually attracted to is probably not the best choice.

The point is to find the feeling and amplify it as much as you can, before you start to extend the metta. 

You can also use logic to strengthen your resolve. You can imagine what your situation would be like, and by extension, what the world could be like if people genuinely wished everyone else well. 

Finally, there is a "backwards metta hack" that a kind monk taught me. 

He explained that for him, metta had been the biggest challenge in his practice. He had a miserable upbringing and major problems with depression, even suicidal ideas, before he was introduced to Buddhism. So when he started out, he simply could not do it. He just couldn't find the feeling within himself. 

However, as he started to learn how to calm the body and mind through meditation, he would experience increased peace and well-being within himself, and had a breakthrough at one time, as he was coming out of a very peaceful meditation and felt very calm, very soft and yet very clear and bright. At that moment, something inside of him clicked: 'What if I can radiate this state?' - and then he started the metta meditation. Immediately, it felt genuine.