Recurring Lack of Compassion

I am trying generally to follow the Mahayana path, with a union of emptiness and compassion. However, I experience clear problems with compassion. These manifest as : 1) general detachment from people 2) spontaneous and stubborn judgments towards others 3) lack of altruistic motivation. I'm wondering how to tackle all these problems. I'm similarly wondering how best to develop compassion, or rather what prerequisites might allow greater feeling and furthering of compassion. Thank you.