What is strategy, and what makes a good strategist?

I know this has probably been asked a billion times, but I haven't yet seen an answer that satisfied me. I've heard strategy defined as "allocating resources to achieve the most effect" or something along those lines, but someone pointed out that strategy had to be defined in terms of a specific goal, because "most effective" is too vague and can lead to missteps. I've heard that strategy defines the win condition, while tactics describe the actions that lead to that condition, but to me that just sounds like a matter of values rather than a skill. What does strategy mean, and how do you know when someone is good at it? If you want me to be specific about the context, I'd say social enterprise and community economics.