I promised nickthefanboy I'd make some tutorials for him... so this is my first ever tutorial. I'm sure once I make more of these, I'll get better at wording myself :p
My original image is the following:
The first thing when making an icon is to have a good enough base. There are plenty of ways to crop an image down, it's just something you'll catch on for yourself. Some people like to crop off center, others like to center, etc. Cropping an unique angle is always a nice way to stand out, but some icons don't allow for such.
Now what you will want to do is make a nice even crop, preferably so the height matches the width. I use another program for my cropping, Jasc's Animation Shop, just because it's easier for me to see the numbers add up there than trying over and over again to make the right size in Photoshop. Several people have their own ways of doing it, so stick to the style you know and love. Once you have your crop set right, resize time!
Now a problem I notice with my version of Photoshop is that whenever I resize a large image to 100 x 100, there's this ugly noticeable border added to it.
See, isn't that ugly?! Don't stress, it's easy to get rid of. Just duplicate the base 1-2 times until you see it fade away. It depends on how light/dark your original image is, but for mine I only had to duplicate it once. You'll want to merge the layers now.
This is the base I have set up for myself:
Now there's several different things we can do from this point forward. My personal favorite is to clear up the image slightly. To do that, you'll duplicate your base and go to filter/sharpen/sharpen, which makes it crispy. Then you'll go to image/adjustments/desaturate to make it greyscale and set the opacity anywhere between 1-40, depending on how clear you want your image. Mine usually are around 20-30% opacity.
Merge layers and you have a much clearer icon.
Sometimes it'll come out a little lighter or darker than you'll be able to work with. To remedy those...
Duplicate layer and set the duplicated layer to multiply. Fool around with the opacity until you get something you like. The magic number is basically whatever you decide on (:
Ta-da. Much darker image to work with!
Duplicate the layer and set the second layer to screen. You'll have to fool around with the opacity, usually around 50% helps with this.
Then you'll duplicate the base again, dragging it to the top. Set this new layer to soft light, fooling around with the opacity again.
For this look I did 50% opacity screen, 60% soft light.
And another fun thing people like to do with their bases is to gaussian blur. You'll duplicate your layer and go to filter/blur/gaussian blur. Set the radius to 3.0 and accept. Then desatuarate the image and set it to soft light.
This effect is really nice when you have used a lot of textures in your icon and would like to maintain some clarity.
Remember these techniques because I'll refer you to this post a lot probably 8)