I've never done an actual Photoshop tutorial before, but I seem to help people with it a lot, so I decided to give it a shot.
This tutorial will teach you the many different ways to achieve a black and white image.
Each way has its pros and cons, and they all work better on different types of images.
I'm going to use the mindblowingly beautiful
Tom Welling as my starter image, because I don't mind seeing six of him. :)
I normally edit my images before resizing them to 100x100 pixels if you're going to use them for that. It's easier to adjust things, because you have a larger canvas to work with. However, I am going to crop this to 300x300 so we can get a basic square icon shape. :)
The easiest way to make a black and white image for me is to select a new layer, fill it with black, and set it to Color.
If you go this route, I suggest further editing the brightness/contrast, and maybe adding a Soft Light layer on top of this.
The next way would be to simply Desaturate the picture. I think most people know how to do this: Image => Adjustments => Desaturate.
I don't recommend turning your images black and white this way, because you lose quite a bit of image quality.
If you use this way, you will most likely need to edit the brightness/contrast a bit more than other ways, because you simply get a greyscaled effect on the entire picture that looks rather dull by itself.
Another rather simple way of making decent black and white images is using the Gradient Map feature.
Image => Adjustments => Gradient Map.
You get a nice contrast using this, but I often find it darkens the image quite a bit, but if it's what you're going for, whoo simple!
If you're like me, you add effects and things after you've made an image black and white. If you know from the start you want a black and white image, regardless of what you add to it later, you can use the Image => Mode => Grayscale setting. Anything you add to the image, be it text, textures, etc will automatically be black and white, so it makes it a bit easier for you as far as that goes.
You get a bit of undercontrast this way, so you will still need to fiddle.
The next way is a bit more complicated, but it gives a nice result.
You can make a Channel Mixer Layer.
In your Layers Palette, fourth from the left, you see a little circle that's half black and half white. Click it, and you get a variety of neat little options. We want to click on Channel Mixer.
There are a lot of different combinations as far as contrast and brightness go this way, just make sure that you have Monochrome checked at the bottom left.
The next way to achieve a black and white image is using the Hue/Saturation menu. Image => Adjustments => Hue/Saturation.
You can simply lower the Saturation slider to zero.
You get quite an undercontrasted feel with this, but it's quick and easy, and if you find that the yellow is rather dark, like in my picture of Tom here, you can edit just the yellow channel from the same menu if you want.
The last way to make an image black and white is to utilize the Lab Color setting.
Image => Mode => Lab Color
Once you've converted your image, click on the Channels palette. By default, it's in the Layers palette on photoshop, just another nifty little tab.
Click on the lightness channel.
You get a very dark contrast with this, and I've noticed that it gives a softer effect to the picture automatically, without anything else done.
Here are all of the different ways resized and side by side so you can see the difference:
If you're a .PSD person, I've uploaded it
here. I don't see why you'd want it really, other than to compare the layers and what they do to the image.
I hope this tutorial helps you! Feel free to
join the community and
friend me if you'd like to see more! =)