Do you know how to do this in writing? And if you're a reader, do you know how writers try to do it? Here's what I find is best: interviews. I interview the character: what's your favorite color? food? sleeping position? sexual position? how'd you get that weird mole on your neck? etc and so forth.
I have, in notes I took in a writing class, a list of about 20 must-ask questions for a character. Also, imagined scenarios--like what drink would your character order in a bar? and how would she or he respond to an intimate question from another patron or the bartender? Something like that.
But I also like to just watch people. I find regular, out-and-about people to be the best foundations for building/creating story characters. Malls in economically depressed areas are rife with fodder for this. And so are malls in ritzy, glamorous areas. Airports and subways are particularly riveting.
I once talked to an actor who told me he does this, too. He watches people's mannerisms and maybe, later, he'll incorporate them into a character. I have another actress friend who based a whole stage character she did on a mutual friend of ours (it went well for the actress; the friend was horrified). And both actors told me they pretty much do what I do when I build my characters: they build whole background lives on their pretend people. Some of what they make up lands in whatever production they're doing; some of it never does, but they know what's going on (in the background of the character's long ago) as they're acting it all out. I will say ditto to this for written characters--some of the stuff I know about a character in a story, only I know; the information never makes it into the story. But knowing it as I write helps keep me straight on the character and his/her motivation and all that.
Here's what happens if you and I go out to dinner (want to? No, I'm serious--want to? I'm totally free Saturday): we'd talk and have a lovely time, enjoy ourselves, etc., but my brain would wander away often from our table. I'd be noting and wondering about the sad-looking lady sitting alone at the bar in an awkwardly-fitted spangly top, absorbed in a Texas-sized margarita (WITH a Corona upside down in it, no less) and speculate about what she's looking at on her phone. I'd be distracted by the couple sitting at the table catty corner ours, because they look miserable, just miserable (what the heck happened? are they breaking up? did somebody lose a job? did they forget their wallets? or seriously, yo. The minestrone WAS really bad tonight).
It's a problem, but I'm good with it now because (a) I find other human beings completely fascinating, and (b) god knows I've worn enough awkwardly-fitted spangly tops and been morose at plenty of restaurants in my lifetime. I'm certain I'd have been written into a Charles Dickens novel had we been from the same era and hung out in the same pubs.
Here's a good example of how minutely detail-oriented I can be when it comes to people watching: I was watching a YouTube interview some time ago with Jason Isaacs (hello to Jason Isaacs!). I remember I wanted to watch it because I'd discovered, on Netflix, a short-lived but fascinatingly excellent police drama series he'd been in that was canceled all too soon (dammit, American TV and American TV watchers--get with the program! Less Kardashians, more mind-bending blue-eyed cop dramas! Is it too much to ask?!). So they were interviewing him and two of the show's creators; it was on a panel-y thing, so they had a pitcher of water set in front of the 3 people. While one of his coworkers was answering a question, Jason Isaacs decided he needed some water, but instead of just pouring himself a glass, I noted he poured the OTHER two people each a glass and THEN served himself. Didn't even ask them if they wanted one, just thoughtfully poured them each a glass, just in case, and then served himself...last. Clearly, this is a person who was raised well. I bet his parents made him do chores. (Note to self: find some chores for M to do.)
Also, I can't remember anything they talked about, which was the whole point of my watching the interview. More info on the show (because I was also reading its pilot episode script at the time, trying to figure out: how does one write a pilot episode script?). But I do remember the thoughtful water pour.
That's the kind of stuff I get distracted by at dinners out, and the stuff that goes into my character building mental bank for later use: I'd use that information to build into a story (or write a story about) someone who's got a lot going on--stuff's happening around him, he's working, but in one particular moment he stops to think about other people's needs first. That's what makes it into the story, and the reader goes: oh, this is a nice person.
What doesn't make it in is the background information I made up that he does this because when he was XX years old, his dad made him get a paper route so he could afford the guitar he really wanted...and one day he got mugged on the paper route and one of his fellow paper route boys went out and bought the guitar for him and it affected him for the rest of his life.
Is that weird? Do you do that? I do worry it's weird sometimes, that I can't always remember what we talked about 20 minutes ago, but I remember that you used your utensils in the European way instead of the American because I wondered who taught you to do that, where you learned it, and why you felt McDonald's was a good place for it. (No judgments here: I once ate midnight breakfast at a Waffle House with a Scottish person who did this, and found it utterly charming.)
One last thing before I sign off to go stress myself out with grades and parent-teacher conference preparation:
Evil characters. Let's talk about how I think all writers should being do those, if they're interested in doing them well (some writers are not, and that's fine too...I just won't find your antagonist very believable). I think the most important aspect to an evil character (or someone in a story who's just really, really antagonistic) is to sprinkle them with a bit of angelic dust. I just saw a quote earlier today about how Satan is actually lovely to look at; not at all the hideous, red-horned monster he's usually depicted as, and that we should all remember this because evil walks amongst us often in beautiful disguise. Perfect summary for how to build a crazy ass evil antagonist. I mean, even Hitler painted watercolors.
(I wonder what George W. Bush's one good quality is?) (GASP! I'm sorry! I'm very, very sorry and I apologize for that last bit, for bringing up politics--were you eating? I'm sorry if you were. I have angst about George: first, I think we're related--one of my ancestors is Henry Sampson, a Mayflower pilgrim, and I think George's mom Barbara is also related to that guy. Which makes George and I like 200th cousins 1,000 times removed or something. Second, he always seemed like a lovely man--someone I'd enjoy talking to at a cookout, even if he was helping to master mind war crimes and all.) (That last part just proved my WHOLE point about how to write a good evil character. Score!)
And, conversely, you should do the same with protagonist characters--give them some flaws. I mean, nobody's perfect. I look at myself in the mirror every single morning and go: "You're going to be PERFECT today, Amy. You're going to use your time wisely, get your work done, leave early with everything ready to go for the next day, cook a gourmet meal, clean a bathroom, do a perfect bedtime routine and write 10 pages tonight. PERFECT. Get going!"
And then I hang out on Twitter half the afternoon, blog instead of finishing up my grading needs, nothing's ready at work for tomorrow, I'm eating take out right now, my bathrooms are possibly harboring Ebola, I'm thinking we're going to let bath time slide tonight, and I will have only written this blog entry.
But I'm not as beautiful as Satan, and so you know. Small blessings.