Step One:
As per usual, first things first. Open up photoshop, and create a new document. If you want to use this technique for a proper logo that you will definately use, i suggest you make your canvas size very large, so that quality isnt lost when resizing. But.... for this tutorial, to save space i will make mine 500px x 500px.


Step Two:
Make a new layer, call this layer "cog". Now grab your Rectangular Marquee Tool(M) - ensure that it is the rectangular shape, not circle or column etc. Now, make some simple rectangle shapes, all on the same layer "cog". Dont go too over board, other wise your logo will look really bad, but don't be too reserved! You can go back to this step later if the result is not what you want. This is also the part that make every single attempt different and unique, so please play around with this to see what you can come up with.
This is what mine looked like:



Step Three:
Lets make that boring shape a little more interesting! Making sure that your "cog" layer is selected, go to Filter >> Distort >> Polar Coordinates....
A little popup will come up, make sure the circle next to Rectangular to Polar is selected, and press OK. That should result in something along the lines of:



SIDE NOTE: If you pay a bit of attention, you will notice a few things.
-If you make a rectangle near the top of your canvas (in Step 2), it will result in a smaller circle/arc near the centre of the result (in Step 3).
-If you make a rectangle near the bottom of your canvas (in Step 2), it will result in a larger circle/arc near the outer ridge of the result (in Step3).
-If you make a rectangle that spans all the way across horizontally (in Step 2), it will result in a circle in the result (of Step 3).
-If you make a horizontal rectangle and cut it (in Step 2), it will result in an arc, or circle with missing pieces, in the result (of Step 3).


Keeping that in mind, you may want to go back to step 2 and revise your shapes


Step Four:
To make this logo a little more modern or "cooler", we're going to make the cog shape 3D.
Before we do our perspective changes, we need to position the cog in a way that looks nicer, where we can see a lot more of the side when text is placed on top of it. Edit >> Transform >> Rotate, a box will apear around the cog shape, click on one of the corners and spin the cog around until you have the most detail on the left hand side and top side. Press Enter when you're done.



Go to Edit >> Transform >> Perspective, that box will apear again. Grab one of the top corner, and drag it towards the oposite side. I.e. Grab the top left corner, and drag it towards the right hand side. This will put a little perspective on the shape. Like so:



Press the Enter key to confirm your changes, or double click on the shape. The width of the shape is now ok, it has a little bit of perspective on it, but it doesnt really look right. Go to Edit >> Free Transform, the same box will apear, click and drag the middle top anchor point and drag it a bit down. Drag it untill it looks a little more natural, and so it looks like its on a surface, being looked at on a lower angle. Press Enter when it looks good.


Step Five:
Onto some colouring now. (Dont worry the 3D isnt done yet, we need colour to continue with that). Make sure that your cog layer is selected, right click on the layer and select Blending Options. Fill in these settings:




Step Six:
That's the colours behind us, and all preparations for making the cog 3D. If you're not entirely happy with how the perspective or angle looks, please make alterations NOW, after this step it will be too late. Review Step Four, for instructions on how to rotate, resize and change perspective.
Select your cog layer. Make sure that your Move Tool(V) is selected. Now, while holding down the CTRL + ALT buttons, press the up arrow key. As you can see, the cog is duplicated, while being moved upwards by 1 pixel - essentially creating a height for the shape. Continue doing this until the height looks natural. 10 nudges was sufficient for me.


Step Seven:
It still looks a little flat. Select the very top layer, right click on it and click on Blending Options. Use these settings:

Now select the very bottom cog layer and apply these settings:


Step Eight:
And thats pretty much it! Just play around with text on top of it.



FINAL RESULT: