Moral self-knowledge is an unruly beast that cannot, I think, be trapped and held still for systematic examination, partly because moral self-examination is itself a moral act, tangled up with the very traits under consideration. The jerk will tend toward a biased self-examination; the sweetheart will be biased in a different way; and the conclusions one habitually reaches, on either side, can reinforce or undercut the very traits self-ascribed. "Oh, I'm such a sweetheart, so much nicer than everyone else around me" is not, in most circumstances, a thought that sits very comfortably on its bearer.
The usual method by which we consider our moral character -- trying an adjective on for size, as it were, and asking, "Is that me? Am I trustworthy? Am I kind? Am I gentle?" -- is, as suggested by both informal observation and psychological research, a method of little probative value. Maybe somewhat better is taking an icy look at objective data about yourself or asking for the frank opinion of someone whose judgment you trust -- but both of those approaches are also seriously flawed.
So here's another approach to add to the stock -- an approach that is also flawed, but which deserves attention because its potential power hasn't yet, I think, been widely enough recognized. Look at the faces of the people around you. Central to our moral character is how we tend to view others nearby. The jerk sees himself as surrounded by fools and losers. The sweetheart vividly appreciates the unique talents and virtues of whomever he's with. The avaricious person sees the people around her as a threat to her resources (time, money, but also possibly space in the subway, position in line, praise from her peers). The person obsessed with social position sees people who vary finely in their relative social standing. Or consider: What do you notice about others' physical appearance? This reveals something morally important about you -- something not directly under your control, a kind of psychological tell.
Or so I think it's reasonable to suppose. I'm open to counterevidence, e.g., by experience sampling beeper methods, combined with some plausible related measures of moral character. But psychological science isn't there yet.
Of course you can game it. You can sit around and work yourself into a blissed-out appreciation of all those wonderful people around you, congratulating yourself on your sage-like moral awesomeness. This is a misfire, especially if there's an implicit (or explicit) comparative dimension to your moral self-assessment as you do this. (If only everyone were as good at me at seeing how wonderful everyone is!) Or you can choose to recall situations, or choose to put yourself in situations, disproportionately suggestive of the type of moral character you'd like to see yourself as having.
But I don't think it's inevitable that we game the method. I find it interestingly revealing (and disappointing) to look at strangers in the store or acquaintances at a party, letting my relatively uncensored assessments of them float up as an indication not of anything about them but rather as an indication of something about me, that I view them that way.
You can also notice things post-hoc: You can catch yourself viewing people in the way characteristic of the jerk, or in the way characteristic of the avaricious person, or of the person focused on status or sexual attractiveness.
It needn't always be negative. Sometimes you can congratulate yourself on being the one person in line who seemed to treat the cashier as a person. Sometimes you can feel good about the fact that you find yourself feeling good about the people around you. But I emphasize the negative for two reasons. First, I suspect that non-depressed people -- perhaps, especially, relatively affluent Western men? -- tend to err toward having too high an opinion of their moral character. Second, there's probably something cognitively or morally unstable, as I've gestured at a couple times above, about using this technique primarily for moral self-congratulation.
[Jeanette McMullin King has reminded me of the poem "The Right Kind of People", which fits nicely with this post.]