When you only want one part of an image to stand out, such as a person, blurring the background really helps. To do this, duplicate your base, and erase the background on the top layer, simply leaving the part that you want to stand out on that layer. Then go into the bottom layer and blur it. You can either use Motion Blur, (Filter-->Blur-->Motion Blur) to get an effect like in this icon:
I normally hit Motion Blur several times to get a really prominent blur. Alternatively, you can Gaussian Blur (Filter-->Blur-->Gaussian Blur) the background, to get an effect more like this:
With these three icons, I also upped the brightness and lowered the contrast (Image-->Adjustments-->Brightness/Contra
Another good effect is to add brushes to the background, behind the image you want to stand out, like so:
As well as Motion Blurring the background, I added a grid brush behind Frodo also.
Brushes are exceedingly useful things. You can read more about them in my tutorials here and here. You can also get them for yourself at 100x100_brushes. All my icons use brushes, except the older ones, made before I had discovered them.
You can improve the quality of an image quickly by adjusting the brightness and contrast, and also lowering the saturation. I used this technique heavily in this icon. It doesn't always do an image justice, though, but it's a quick way to improve the look of your icons.
I lowered the saturation a lot in this icon, too:
The Variations option is a great way to add different effects. (Image-->Adjustments--Variations)
With these icons, I added Yellow and Red to the original base to get this warm, bright, orangey effect.
If you desaturate the blank first (Image-->Adjustments-->Desaturate) you get a very different look.
More Red x1, More Yellow x1
More Red x1, more Yellow x2
You can add whatever colour you want to the icon, though, for example:
Heavy on red -
Heavy on cyan -
Heavy on yellow -
Rainbow effects look great, and are amazingly easy to do. Simply right click on your icon, and click on Blending Options. Then highlight (don't just check the box) Gradient Overlay. You will have a selection of Gradients to choose from. For these icons I chose a strong rainbow gradient, changed the Angle to -145 and the Blend Mode to Soft Light. Alternatively you can simply adjust the opacity, or use another Blend Mode. Experiment with the Blend Modes and different Gradients until you find something you really like.
These ones use, in turn, paler gradients (lower opacity) and a different shade of gradient to give a sunkissed look. With many of these icons, I desaturated them before I applied the gradient.
Text effects: Go back into the Blending Options box (where you adjust Gradients). You can add Outer Glow, which is always nice (and you can adjust the colour to make it more subtle), like so:
Alternatively, you can outline the text using stroke which looks especially good with Pixel Fonts like in these icons. With these, always make sure the anti-alias on your text is off (set to 'None' instead of 'Strong' or 'Smooth' or whatever). I normally use the colour black, or at least a dark shade, because I think it looks better with a paler inside, and with the size set to 1.
It's worth experimenting with the other options in the Blending Options box, like Drop shadow, or Bevel and Emboss/Contour/Texture/Satin - all of which I used in the banner for this icon journal to give the text a 3D effect. This style looks best on large text, I think.
I think that's enough for now! I hope these might help you guys out a bit. It's also worth going through the memories at icon_tutorial and following some longer, in-depth tutorials. I try to follow the ones posted quite a lot, and I always learn something new, as everyone makes icons differently.