We’re going to make an icon like this:

1. Open an image, select the part you want to use (I usually use the rectangular marquee tool holding down the shift key on the keyboard to have a perfect square), copy it (ctrl c), open a new document (ctrl n then click ok), paste it (ctrl v), resize it to 100x100px.

2. Add a New Fill Layer: Layer –> New Fill Layer –> Solid Color… write 0b005f in the color palette; set this layer to mode: Exclusion, Opacity: 50%;

3. Add a New Adjustement Layer: Layer –> New Adjustement Layer –> Color Balance… with these parameters:
Midtones:: Color Levels: +43, -10, -15 with Preserve Luminosity checked;

4. Add a New Adjustement Layer: Layer –> New Adjustement Layer –> Brightness/Contrast… with Brightness:: +22 and Contrast: 0;

5. Add a New Adjustement Layer: Layer –> New Adjustement Layer –> Selective Color… with these parameters:
Reds: Cyan: -78, Magenta: +41, Yellow: +28, Black: +47;
Neutrals: Cyan: +19, Magenta: -8, Yellow: -19, Black: -1;

6. Add a New Adjustement Layer: Layer –> New Adjustement Layer –> Brightness/Contrast… with Brightness:: +8 and Contrast: +32;

7. Add a New Fill Layer: Layer –> New Fill Layer –> Solid Color… write ffe3fb in the color palette; set this layer to mode: Soft Light, Opacity: 40%;

8. Add a New Fill Layer: Layer –> New Fill Layer –> Solid Color… write ebf4ff in the color palette; set this layer to mode: Soft Light, Opacity: 25%;

9. Add a New Adjustement Layer: Layer –> New Adjustement Layer –> Brightness/Contrast… with Brightness:: -14 and Contrast: +18;

And you’re done!

Other Exemples with this technique which can be found in my Avatar page