Don't forget to BACKUP!
1. Backup of your current working ROM via ClockworkMod (just in case anything goes wrong)
2. Titanium Backup of all your Apps and their settings
3. Backup any SMS messages you want to keep.
4. Backup your contacts (unless you solely use google as your address book)
5. Backup your SD card (just in case anything goes wrong!)
I would also recommend doing EVERYTHING (wipe & flashing) in Recovery. I have never had a problem since I started doing it manually.
Download all the files via your phone (they will end up in SD Card/Download). Probably best to start with stable, backup, and then play with nightlies
CM7
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Gapps
Latest Version/Google Apps - CyanogenMod Wiki
In ClockworkMod Recovery
Advanced/Wipe Dalvik Cache
Advanced/Wipe Battery Stats
Wipe Data/Factory Reset
Install Zip from SD Card - Flash CM7, then immediately flash Gapps WITHOUT rebooting
Reboot
Giggle when you see the new bootanimation
Wait
First boot takes a while, don't freak out!