Originally published at: http://www.howtogeek.com/162516/how-to-flash-your-nexus-s-or-any-other-android-device-with-a-new-rom/
When you bought your phone it was cutting edge, had the latest version of Android, and made your heart sing. A year or more later, it doesn’t get the new updates and the performance is a little sluggish. Breathe new life into your phone by flashing it with a new custom ROM.
Good article. Lot's of valuable information. However, TWRP Recovery is better than Clockwork Mod!
I just did this recently. The "Nexus Root Toolkit" is pretty useful; it's a Windows application which does all of the driver and backup operations, as well as a "root my device" button.
Word of (minor) warning. The Gallery app's for each Album shows the images in the descending date/time order, with newer images at the front. If you back up your pictures by manually copying them in Windows Explorer (MTP mount, drag-drop) and then bring them back after rooting, all of the images will get a NEW time stamp of the time that they got copied to the camera. Your images will no longer be in the order you took them.
The Nexus Root Toolkit offered to back up the images for me, but never seemed to be able to do it. Perhaps it would have been successful - I don't know. Or: PTP might have kept the dates, while MTP didn't.
I just used the "Nexus Root Toolkit" to flash my Nexus S. Thought I followed it thoroughly. All seemed to go according to plan until I rebooted. The phone opened showing an image of CyanogenMod. That's it. It does not reboot.
What went wrong?