What Steve said is certainly the best way to to clean away unwanted tracks. And normally the best way to back up projects..
But! just in case, and this has happened to me, you actually change your mind and you want an old discarded take, then you should also have back ups stored somewhere with everything still stored. This is done by drag and drop or copy paste to a new location. Of course no point keeping bad takes.
And so another thing to keep i mind is to always name a track BEFORE you record it.
Naming tracks afterwards doesn't show in the audio folder.
I have default templates with extra tracks already named
Bass 1 , Bass 2 Bass 3 , Gutar 1 Guitar 2 etc.
This way if your ever digging for audio in the folder they will be easier to spot. Sonar adds those seemingly random numbers which I'm sure nobody's ever been able to decipher.