How to disable file associations to an app before/after installing?

Solution 1:

lsregister is the command to deal with Launch Services. To unregister an app use the -u option and the path to the app bundle. lsregister is not in the PATH - you have to use the full path to the executable:

/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -u /Applications/MediaPlayer.app

Solution 2:

Select a file type that you are having this problem with and right-click the file. Select 'get info' for that file. The 'get info' window has a section labeled 'open with' and you can check if that app is set to open that file type. If so select another app to open that file. Under that option is another option to save that info for all files of that type. Be sure to select that option.

If this was unclear let me know and I'll try to explain it better.