Go to the developer's folder, and in About Xcode.pdf they will have instructions
/Developer/Developer/About\ Xcode.pdf
This is near the end of the pdf, but you can search for uninstall and it will give you some options
You most likely want
sudo <Xcode>/Library/uninstall-devtools --mode=all
But I recommend that you read the removal section so you can see the options available.
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