Just as with a real flower, you can tear off petals and drop them to the special area called "the Collector":
In addition to drag-and-drop, you can put files and folders to the Collector by selecting thecommand from the item's context menu, or by pressing ⌘⌫ hotkey while pointing to an object with mouse.
No files are harmed until you click thebutton.
Once all unneeded files and folders are in the Collector, just clickto actually delete them.
You can expand the Collector by clicking on it to make sure you are not about to accidentally delete some needed files. The expanded Collector works just like the sidebar, so you can preview files and drag them out. Another way to get an item out of the Collector is to point and click thebutton near its name:
Some folders like /System, /Library or current user’s home folder cannot be deleted, so the Collector will not accept them. Semi-transparent (consolidated) petals also cannot be removed: you’ll have to expand the group and drag individual files and folders.
Clicking thebutton starts the deletion process, but don't get scared: you'll have 5 seconds to change your mind and press :)
The files and folders are deleted permanently, not moved to the system Trash, so that the disk space taken by them is actually recovered.