I'm wondering how you generally go about describing a character that you have just introduced, be they main, secondary, or tertiary supportive but with names (e.g., a co-worker in a store that your main character is being introduced to but will seldom interact with). I personally find it annoying when someone starts out with a giant paragraph introduction, but I fear I may have gone too far in the other direction with only mentioning physical characteristics when they become important or are used in some way (e.g., "Mike brushed his long, brown hair out of his eyes."). What's a good balance? I'd like my readers to have at least some idea to go on in terms of how I envision the character, but I don't want the plot to get lost in lines and lines of adjectives.
I prefer the method you've adopted. Mention the important characteristics. The reader is going to develop his own vision of the character, regardless, and too many details just interfere with that.
I agree, no matter how detailed you describe the character, the reader will always see it differently from you. Things like eye colour and hair colour will put the reader on the same track as you, in terms of imagining that character.
A good way to point out character without saying it outright is using subtle details about their room/home/office/car. If they MC has steps on a pile of clothes in the morning and uses said pile to dig out a shirt to wear for the day the reader will instantly recognize that the MC is a slob and/or lazy. Let the actions of your character do the talking. After all, they do speak louder than words .
I tend to dislike the "sneak it in" method, as in your brown hair example. The fact that his hair is long is relevant, but the fact that it's brown isn't, and the fact that it's long is sufficiently hinted with just "Mike brushed his hair out of his eyes." I prefer to be explicit, but _very_ short. As in: Joe said, "Jane? This is Mike." I looked up from my artichoke and considered Mike. Tall. Brown hair clipped army-short. Nervous-looking, but with a nice face. Not bad. "Hi, Mike. Have a seat." ChickenFreak
Find a plot-relevant reason to be describing them. In my series the weather's always moving as there are gaps of a month or more between the stories, so it's easy to throw in how hair and dress are affected by that. Also one of the books is set at the prom. You cant write girls going to the prom without mentioning their dresses. I'm actually dreading writing that part - so far the only one in the series I haven't written parts of yet. Basically, describe someone as much as you like if there's a reason to. First impressions are fine for a run down of the character to get some basic details in. If it's best friends meeting you have to be more careful. After my introductory weird ramble from my narrator of the time, the 4th book starts with a whole conversation about the characters' hair. Writing teenage girls makes it too easy though. When writing my male main character for my previous novel I had to work in actual *lament* before he would tell me what his best friend looked like... Sarcasm for other characters, but he needed to be mourning the guy to be prompted to give us the run down of something as basic as hair colour.
Since we don't live in the days of Dickens anymore, it's better to keep things shorter, on average, so it seems you're going in the right track. It's better to mention a very few but distinct and interesting characteristics, ones that will carry the reader's imagination away. Likewise, having them mention the physical characteristics while doing some more character-specific habitual action - like the "Mike brushed his long, brown hair out of his eyes." example you mentioned above - is a great way to show physical attributes, perhaps hint at emotional/mental attributes, and also make the character go around doing something instead of just being described.
My characters have very little by way of physical description because it plays very little part in later events. I find that this is a trap that many writers fall into: Spending too much effort describing inconsequential details. Unless he's an exceptionally vain character, or unless there's a part in the story where someone says "HELLO, YOU HAVE BROWN HAIR THAT IS LONG." then you're wasting your reader's time.
But I feel disconnected from the story if I don't get any details at all about how the character looks like. Hair colour and eye colour is fine or a feature that stands out. The writer could easily weave it into the narrative...instead of having someone say they have brown hair...
If it's a narrative in the first person I think about the things I notice about people when I look at them and note them down, I usually find hanging out in a cafe and 'people watching' on the passers by is quite good for this, because then you're experiencing what it's like to observe someone only briefly and picking up on what's significant about them. Think about when you're describing a person in real life to someone else. If I'm describing my friend Emma to someone for example I might say, "You know Emma, dyes her hair red, slim, she's wears glasses" because this is what stands out about her to me and makes her different from a lot of my other friends.
find a significant detail that shows something about the character without saying it in so many words. something in his looks or way to speak or act that says more about what kind of person he is than just what it's suggesting. Im bad with examples but I hope you know what I mean...
I avoid unnecessary character description, and limit it to what the POV character would notice (not merely passively observe) at that point in time. For example, I wouldn't mention the character's height or build unless it had changed noticeable from when the POV character last saw him or her. The same with hair or eyes. And the mirror stunt for a first person character is overused and painfully transparent. Leave it to the reader's imagination unless it's truly necessary to paint a picture.
I usually start with action of some sort, then give a proper introduction of the character a few paragraphs in... when the reader is hooked. "Janine was small girl, seventeen years old. With long and curly blonde hair and narrow blue eyes. She'd rarely be seen wearing anything but jeans and simple tops." That's pretty much all that will be mentioned about her looks for the rest of the story.
If your character has issues with being short, there'd be no problem mentioning how tall people are because that would be noticed. Skinny people get noticed, or large ones. If your character has self esteem issues, they can show through the description of others. The 'sweeping his long hair back' only works if you add an attribute like 'unruly', 'sleek' or 'greasy' - that let's us observe vanity or lack thereof, and gives us not just looks but also attitude. I like how L Hamilton describes people by their most distinct feature until the name is learned. She'll call someone 'the suit' or 'ponytail' etc. It's visual, fun, and usually tells as much about the observer as about the person observed.
To describe a minor character quickly, use a character signature. 'She wore a scarf like a piece of chewed string'. Whenever the character re-appears, refer to her 'skinny/dismal/bedraggled/etc' scarf. The reader remembers her at once. Of course, you can go too far and turn the character into a caricature. Dickens was a master at making a 2-dimensional nonentity into a rounded person, with a few tricks of phrase. Problem is, the nonentities sometimes stole the show!
Okay, I think I have a better approach now. In this case, Michael is my main character: "Kira and Michael were introduced, Michael finding Kria's youthful face, single hoop earring, and short red hair almost fairy-like." So, I have a quick observation from the main character, a VERY brief description of only a few things (not, "he saw she was 5'6", 140 lbs, ...."), and this introduces a slight potential of a red herring for the reader (since the story is fantasy and involves fairies at some point). Also, my naming scheme based on the 3 main characters' place of work are names from different Star Trek series. So this particular character, Kira Naraya, is obviously from DS9 and as a nod to the 1% of readers who will pick up on it I've included in the description some of the defining physical attributes of the DS9 character.
I say, use dialogue and actions as much as possible. From what I'm understanding about modern writing, too much description just bogs down a piece.
I think in modern literature, you've got to be more sneaky with descriptions. You've got to slip it in there so that the reader doesn't feel like we are reading a bio. I'm with a lot of people here - I only describe my main characters. Secondaries are only described if it is in support of a main or if it is something that s/he is noticing about them. For example... "I didn’t even have to look at her face, which was identical to mine both in looks and tragic expressions, to know I was being glared at." In the prior paragraph, my MC noticed that she was being inspected by her sister's bright blue eyes and in the next paragraph, the sister "bounds off in a flurry of curly blonde hair."