Create a new document 250x250, select the "elliptical marquee tool" and draw out a circle.
Fill with a "radial gradient" with your 2 chosen colors, I've chosen 2 shades of blue. (#295ea3 and #214b83).
Create a new layer under your blue circle (or what ever color you have chosen). Hold down "ctrl" and click on your blue circle layer to make a selection. Then goto "select > modify > expand" expand it by 8 pixels. Now fill the selection with a grey color.
Now hold down "ctrl" again and click on the blue circle to make a selection again, click on your grey circle layer and hit the delete key. If you hide your colored circle layer you should have this.
Now add these layer styles to your grey ring shape.
You should have something like this.
Now select the type tool, a nice bold font and a font size of about 200, then type your symbol I've used a "!" sign, you could also use a picture if you wanted.
Now right click your grey ring layer and goto "copy layer style", then right click your text or logo layer and goto "paste layer style", you text or logo should turn out like this.
Now select the "elliptical marquee tool" again and draw out a smaller circle at the top, and fill with the color white.
Set the opacity to 15% and add a layer mask.
Duplicate your layer, press "ctrl +t" to enter into free transform mode, resize your white circle, make it a bit bigger and place slightly above your other one.
That's it all done, here's a few more.
