Black salt is primarily a protective magical tool. I like to sprinkle it around the perimeter of my property a few times a year to keep unpleasant people or things from crossing into my yard. You can also use it at work — tuck a small bagful under your desk to prevent annoying co-workers or the office bully from hanging around. If someone you dislike is leaving your home, wait until they are gone, and then follow along where they walked — toss some black salt into their footsteps to keep them from returning. Dress a black candle in oil and then roll it in black salt and use it in spell work for banishing negative entities or people.
If you have got leftover black salt after a working, depending on what you have used it for, it is something you may want to go ahead and get rid of. To dispose of black salt, if you have used it in a hexing or banishing, take it someplace far from your home and bury it, or throw it into a fire. If you have simply used it for a protective boundary, you can bury it on your own property.