Up to this point in my education, I have had very little exposure to the language and machinery of category theory, and I would like to rectify this. My goal is to become conversant with some of the standard categorical ideas; I want to be able to think categorically. What are some suggestions people have for the best way to go about this? Would it be better to take things head on, and read something like MacLane's Categories for the Working Mathematician? Or would it be better to study category theory via its application to a body of ideas that I'm already familiar with, such as representation theory? How have you learned to think categorically?
—EDIT—
Thank you all for the responses. To clarify, my interest in category theory is more of a means than an end – I want to be fluent in understanding and crafting categorical arguments in other contexts. Although I'd love to be persuaded otherwise at the moment I'm not necessarily interested in studying category theory in its own right; somewhat analogously to how one should be well versed in the language of set theory, even if they do not intend to study sets in and of themselves. Thanks to your responses, I have plenty of material to look at.
Best Answer
I suggest reading Barry Mazur's introductory article "When is one thing equal to another thing?", found here http://www.math.harvard.edu/~mazur/preprints/when_is_one.pdf