If you are re-setting your Lumia, and your phone seems to get stuck at the spinning gears for a long time, try the following:-

Hold Volume Down + Power Button for 10 seconds. Then, when you see the Nokia screen, press the following buttons, in sequence, one at a time:

Volume up
Volume down
Power key
Volume down

The gears will spin for about 5 minutes and then will reboot to the welcome screen and stuff.

You may have to try this sevral times - just have patience. I seem to remember I had to try about 10 times, before my phone finally sprung to life.

Kudos to Alexandre Chohfi - Nokia Developer Champion 

There is now an alternate method if all else fails -  How to easily fix the Lumia reset spinning cogs at home courtesy of My Nokia Blog

Originally posted 13/Sep/2013