So we're going to get into the nitty gritty of how to get it done, and what you'll need to do it.
Pencils: It sounds pretty simple, but I'm going to go over the basics once more. It's always good to have a handy supply of pencils with different leads. I'm not suggesting that you go out and buy a set from 9H to 9B, but have a good pencils for drawing (most artists usually use 2H up to 4B range). I find for drawing hair, having a mechanical pencil around can be handy - especially if your lazy like me, and hate sharpening your pencil a hundred times (each). I actually do almost all of my work with my mechanical pencil and using 2H, B and 2B leads.
Paper: For any drawing, using good paper is essential. In this case, we're going to be doing a lot of layers, adding pencil, and erasing, so you'll want a paper that can take a bit of a beating. My favorite is to use 90lb paper. It's thick enough that you could do just about anything to it, and it won't wrinkle or crease. The thicker the paper the better chance you won't erase through it. Plus the texture really holds lead well and you won't have to work hard at getting dark tones.
Erasers: I usually use a big white vinyl eraser for big mistakes, but whichever you prefer is fine. One thing that I will highly recommend is to get a 'Tuff Stuff eraser stick'. It's a wonderful pen style eraser that works wonders, is under 5 mm thick, and is fantastic for picking out highlights. I can't stress enough how much I love my Tuff Stuff! It's essential for any art kit.
Blending Utensils: Sure, you can be old fashioned and use your fingers, but realize the oil from your hands can damage your drawing. I prefer to use my stump (aka stomp) which is essentially a rolled up piece of paper that looks like a pen. They come in all sorts of sizes and are dirt-cheap. It's always a worthwhile thing to have.
Dusters: Optional, but nice to have if you have the habit of smearing your drawing with your hands. If you don't have one, remember to blow or shake your drawing the get crud off... never wipe it away with your hands! (I've had many smearing disasters. Not fun.)
Whew! Now that that's done let's move on to the fun stuff.... let's go drawing! *cue cheesy music*
Step 1: Layout : Putting Down the Foundation
Here I've started with a face already drawn in for simplicity's sake. I figured I might as well throw it down on the paper to start off with, so you can see the light source I'm working with, and so it won't end up being hair floating in a void in the end.
As you might imagine, the first thing you have to do is block in the hair. I've gone for a semi-curly windswept look for this one, to better illustrate how hair can by dynamic and wild. But chose whatever you're in the mood for, and go for it. While your blocking in the hair- Go crazy! Hair is erratic, fluid, and never does what it's supposed to, so make your hair interesting. Just remember, as your establishing your layout, that you're not drawing hair strand by strand. That is the primary pitfall of artists when it comes to hair. Hair, like the rest of a drawing, is chunks of light and shadow, so treat them as such. Keep thinking about big blocky clumps, and the motion of hair, not individual strands.
Also, keep in mind the environment. I say environment instead of just lighting, because when your drawing hair, you also have to take into consideration where the character is, what movements he/she is making, and how those factors would make the hair react. Try to see the motion in the hair when your picture it in your mind. Keep these things, as well as light source in mind while working on your layout
Step 2: Establishing Midtones
In this stage it's really important to consider your light source. Where's the light coming from? What would be light and what would be dark? Start establishing these differences in your drawing, concentrating mostly on the medium grays at this point.
Don't worry too much about what your pencil work looks like. This drawing will be going through quite a bit of layering, so it doesn't matter if it looks unrefined or sketchy. In fact, if it is sketchy, you're on the right track! Sketches have a natural spontaneity to them that do wonders for hair and motion.
Also, I'll have a quick word on hair color. Even bleach blond hair will have near-black shades, the same way black hair will have white highlights. When your dealing with a grayscale picture, I find it's more important to properly define and render the hair, the be true to the 'color' you want. That being said, if you want a 'blond' look, simply draw most of the hair in lighter tones of gray, and make them darker for brunette. If your confused, just open up a random picture in PhotoShop or Paint Shop Pro and make the image grayscale. Sometimes you can tell what the hair color originally was, but others you can't. Decide if the color will be a priority for you, and then do what you feel is needed to achieve the look. Intuition is a big part of the art process, and shouldn't be ignored.
Step 3: Finding Shadows: Darkening It Up
Me? I like them dark. So dark in fact, sometimes I whip out a black pen to make sure they're as black as they can possibly be. Why? Because, contrast is important. It's what makes a picture eye-catching, adds depth, and defines it. The only downside to keep in mind is that black, on it's own, tends to look flat, so keep the areas to a minimum. If you're unsure of where to use your darks, find pictures of hairstyles, and squint at them. I know it sounds kooky, but bear with me for a moment. When you squint at the picture you loose definition, but you gain shapes. And by doing this you'll be able to really pick out lights and darks, and the shapes the hair can make, without worrying about the details which people like me get bogged down in.
Remember, you're still not drawing individual strands; you're drawing shapes and tones of lights and darks. And, as always, when you're putting down your darks, keep in mind your light source. A picture with very dramatic light sources will have more contrast and heavier shadows, unlike this piece here, which has glamour lighting (glamour lighting is a photography term which basically means 'soft light'. Generally it's a main light, with a pretty strong fill light so there aren't many striking blacks, but most importantly, it makes the models 'look good'.)
Step 4: Blending In: Softening the Piece
Don't really worry about loosing some detail, that's part and parcel of this step. We need to smooth out all the sketchier pencil applications to create a more polished look. But use your common sense, if you feel your loosing too much of the drawing, use a lighter touch, or try another blending tool. Keep in mind, that as you blend it all together with the stump, the picture will get darker. Don't worry, it's a good thing! The more layers you have on the paper, the better step 6 will be.
Be careful and test the waters when you start blending, depending on how soft a lead you've used, and what tool you use to smudge, it will be easier or harder.
Step 5: Refining Details: Rendering the Hair
Okay, now you can start drawing lines! But don't flatten out all those beautiful tones you've created! Vary the pressure, make darker lines in dark sections, and lighter ones for the lighter. All you're really doing in this step it to make the image crisper and give it a more 'hair-like' texture by adding some detailed line-work. You're using the lines to enhance the hair, not to overpower it. Still keep the chunks of hair and motion in mind, but make them sharper and clearer on paper.
If your like me, and have made the darks as dark as can be, you may find yourself asking, 'how do I add detail to this? My pencil won't do any darker'. Well, as I mentioned earlier, I sometimes use a Staedtler .005 drawing pen to add really fine black details. But be careful, and use it sparingly. You can't erase it like pencil, and erasing is very important in the next step.
Step 6: Finishing Touches
So, take out you Tuff Stuff eraser. If you don't have one, find another eraser (not a vinyl one, they're generally too soft for precision erasing) and slice the end with an Exacto blade so you can eraser really sharp fine lines.
Now, go crazy and pick out the highlights! Remember, you can always vary your pressure to get softer or more striking highlights, so use a nice range. And if you make a mistake, you can always add more pencil.
Just remember, with dramatic lighting (not like this picture) less is sometimes more. A few well-placed highlights on mostly dark hair can have a very striking effect.
And for a final, final finishing touch you might want to add some fixative to it. Time can do some devastating things to a work of art, especially if it's in a well-traveled sketchbook. I like to use Krylon's Workable fixative. It adds a nice protective coat without changing the image at all. Just be sure to spray in a well-ventilated area, or you'll be woozy in no time! Also, going with a fixative that says 'workable' gives you the added bonus that if you want to change something later down the line you can- without ruining the drawing.
Tips and Tricks
As always, view hair as fluid and erratic shapes, not lines
If you can't erase highlights, use white gouche, or a white gel pen
Don't be afraid to find photo-references, even the pros need them from time to time.
Practice, Practice, Practice
Don't be afraid to not outline your images, not everything has to be liner
Use a lot of medium grays, don't think of your piece as black and white, but as a grayscale image
If a rule doesn't work for you, ignore it!
'Oops, I messed up!'
First of all, don't worry about it. I mess up my images more often then I'd like to admit. Try to think of it as a learning experience rather then a failure. Try to figure out where you when wrong so you won't make that mistake twice.
Don't be ashamed of some of your first attempts, everyone has to start from somewhere. You don't get better overnight. And don't forget to keep working! You'll never get better if you don't practice.