I encountered just one hitch in the upgrade and it was related to the clockwork recovery I had. Here are the steps to upgrade from CM 10.2 to CM 11 Nightly.
Backup your phone data
- Backup your SMS messages. I used the SMS Backup and Restore app.
- Backup your photos. Just copy the \DCIM\Camera folder to your drive.
- Backup your phone ROM. Just boot to recovery (Power off, Hold Power and Vol Up button until the recover menu comes up) and do a backup.
- download.cyanogenmod.org/?device=crespo (cm-11-20131207-NIGHTLY-crespo.zip)
- http://wiki.cyanogenmod.org/w/Google_Apps (gapps-kk-20131119.zip)
- Copy the two files, cm-11-20131207-NIGHTLY-crespo.zip and gapps-kk-20131119.zip to the root folder on your phone.
- Follow instructions on download.cyanogenmod.org/?device=crespo to install the Clockwork Recovery to your phone. (See Installing recovery using fastboot)
- Note that I didn't wipe the data anymore. I just wiped the cache. All my apps and setting remained intact.
- Follow instructions on download.cyanogenmod.org/?device=crespo to install the Clockwork Recovery to your phone. (See Installing CyanogenMod from recovery).