For the past few days OS X is showing me updates for iMovie and it started downloading it. I changed my mind about iMovie and so deleted the application. But still it is trying to update iMovie and started downloading it again. How do I let AppStore know I don't need the update and don't show me future updates for iMove?
If you hold ALT/OPTION, the Appstore (on the purchases tab) gives you an option to cancel the download (assuming it is incomplete).
Depending on the version of OS X you have additional steps may be required to remove the application support files (in /Library/Application Support/).
Appcleaner can be used as well, it does a good job of finding the dependencies; but to enable the removal of system and default applications you need to change the Appcleaner preferences.
I've never needed these options, so proceed with caution.
Another option, but that it is ideal is to let the update run (possibly reinstall it first) and then uninstall it again.
I could suggest AppCleaner for a solution.
You will have two options:
You can select "Applications" from the menu bar on the AppCleaner's window and scroll down until you find the desired application. You may select it(if it's locked/stock app, you may need to click twice faster in the checkbox). Going forward with the procedure by pressing the "Search" button will bring up a list of of all related files. Note that some of them might be locked as well, so the above double-click procedure will apply again.
Note: However, this method may not apply for the stock Applications, so you may need to follow the other method.
I deleted the app with finder. Then I still had the appstore prompting for download iMovie which was irritating so I ignored the prompt to update. Then upon reading advice here I went back to finder/applications and there was a folder labeled imovie 9.09 so I sent that folder also to trash. That solved my problem. Appstore is not prompting to update and imovie seems to be off my Mac now