A little while ago, someone asked me how I make my Naruto bases so crisp and nice looking. As most anime icon makers know, when you're working with images screencaped from television recordings, the quality of the original picture can be quite low. I found this especially true for earlier episodes of Naruto before people started recording in higher quality.
So, here's a really really easy method (that I use all the time) to increase picture quality for 100x100 icons.
Program: Photoshop CS2, but works for earlier versions. Easily translated to PSP as well.
I'm starting with this image. A nice pic of Itachi, but the quality is blah.
1) First, crop your picture accordingly, but DON'T resize it. Here is what I have.
2) Next go to image >> adjustments >> Brightness/Contrast. Drop the brightness and turn up the contrast. How much you decide to do depends on the colors in the image and/or how you want it to look. As long as you remember that the brightness should always be lower than the contrast. This will make your colors more vibrant and get rid of that weird grey tint that a lot of screencaps have. For this image, brightness was -10 and contrast was +25. Here's my result, notice the difference?
3) Now, here's how we really get to increasing quality. Go to Filters >> Sharpen. I know, it sharpens a lot of the "impurities" of the image. But this helps more than something like the despeckle filter.
4) Last step! Resize! And now we have a good quality 100x100 base. ^_^