Here’s an old screencast which I never got around to uploading.

It makes sense to set up a single directory in Xcode where built products and intermediate files are kept. You can blitz all the files at once if you don’t need them, you don’t have to set up manual exclusions for your version control and you can set up the files to be excluded from Time Machine backups.

This was recorded with an earlier version of Xcode, but the steps still apply. Please excuse the sound quality.