This is a tutorial for beginners. A good icon cannot be made without a good base, so let me show you the quick and simple steps for making one!

You should always seek a good-quality image, preferably clear and sharp. You're not always lucky enough to find such images, especially if you're as picky as I am about your subject and you don't a lot to choose from. A certain level of grain and blur is all right, since grain will soften when you resize the image and you can use a sharpen filter to fix the blur. As long as you avoid absolutely horrid quality images, you should be fine. For this tutorial I chose a rather adequate quality screen capture from Pirates of the Caribbean.

The first step is to create an angle. Straight lines are boring, so I always rotate my image (Edit > Transform > Rotate) until I get something more interesting.

Next comes cropping, which is most likely the most important part of icon making. The golden rule to cropping is to not center your point of focus. Always have it off to one side or in a corner. Not only will that look more interesting, but it'll leave you ample space for text. Feel free to crop as much or as little off of your image. Here are examples of different ways to crop.

I like the second one best, so let's proceed with that. The next step, which you can see I've already taken, is to resize your image to 100x100 or smaller, depending on your personal preference.

Time to lighten up! Instead of adjusting the brightness of the base, I find that using layer styles gives you a much nicer result. A basic rule of thumb is to create two duplicates of your base image, set the middle to screen and the top to soft light, and desaturate either one or both of them. But, depending on the brightness and contrast of your image, you may choose to take a different route. Always experiment with different layers and styles until you find a look you like.

Since the image I'm using is quite dark, I decided a layer on soft light wasn't necessary, and only used one duplicate, desaturated and on screen. It was still a bit dark, so I duplicated the background again, and keeping the original color, I set it to screen.

I actually like the darker one better, so I decided to keep that. Though this is a good quality picture, it still needs a bit of sharpening, so I added the sharpen filter. It was a bit extreme, so I faded the filter (Edit > Fade) to 50%.

It looks nice as it is, but I thought I could accentuate the gloominess a bit more by tweaking the color. Using variations (Image > Adjustments > Variations), with the slider one bar to the left of the center, I went more green, darker, and less saturation.

And there's my finished base! When you have a great looking base, it's very simple to turn it into a great looking icon. By just adding a border, a gradient, and a few lines of text, I have a very melancholy icon of Captain Jack Sparrow!