[m12k]

I've struggled with this, but feel that I've made some headway in the past decade, so for what it's worth, here are my two cents (YMMV): I'd say start by conscious effort, and then eventually you can build intuition and 'empathy' in a more traditional sense (and your mirror neurons might even help you understand your own feelings better that way too, as seeing something in others might help you recognize those same things in yourself). Whenever you interact with a person, consciously ask yourself questions like 'how does this person feel?', 'how do they perceive me?', 'what are they trying to achieve?', 'what do they think I am trying to achieve?', 'in what context will they interpret the things I say?' and so on. Even if you won't have a lot of those answers, just making yourself aware that there is information there that you are missing is a valuable step in noticing it - and teaching yourself to care about that dimension of the human experience. Understanding what goes on inside a person is not unlike playing an imperfect knowledge game, e.g. reading someone's hand in poker - a combination of observation, prior knowledge, statistics and logic can help gain you insight into likely scenarios (e.g. "Aggressive behavior is often due to being stressed, or feeling threatened - this person is normally well-mannered, so they are likely under stress right now, so instead of snapping back at them, I could ask them if there's anything I could help with - assuming they normally trust me enough to confide in me"). And read books/blog posts about psychology and what motivates people (e.g. watch stuff like this, https://www.ted.com/talks/dan_gilbert_asks_why_are_we_happy (that book is recommended too) and read stuff like this https://youarenotsosmart.com/ ) - it'll help you think about a mind as something that follows rules and patterns, even if those patterns aren't always strictly logical, and hence it is something that can be understood. Eventually, all these things can combine to give you an intuition (a heuristic if you will) about what goes on emotionally inside others and yourself, and as this becomes a greater part of your world view, you'll also get more of a chance to feel a link between those feelings inside yourself and others (which is what I'd call empathy). I think some people, the "natural empathists" stumble on this by themselves; they've just developed this intuition without ever becoming aware of it - but for a person like myself, I needed to understand it consciously before my subconscious could really catch up and start to work on the domain. But it's totally a learnable skill like all others.