Black obsidian is great for clearing any unwanted energy in your own aura or even your home. One way you can easily do this is by simply sweeping it over your body, passing a piece or wand of obsidian over a particular chakra or your whole body, to help clear your field.
Being such a good stone for grounding and centering, you can add obsidian to any of your favorite grounding practices, whether that's meditating with obsidian in your hand, keeping it in your bag when you go out anywhere, or placing it near your root chakra, which is associated with grounding and security.
Obsidian is often formed into a sphere or wand and used for scrying, divination, and crystal gazing. This can also be great to use in conjunction with any dreamwork you're practicing, if you're into that.
Crystal wands are carved from natural gemstones to form a stunning wand shape. Wands are good to hold when you need focus or clarity. Wands are also used in crystal healing to direct healing energy. The type of crystal you choose will bring that particular crystal's properties. A wand pointed away from the body will tend to draw energy away and a wand or point pointed towards the body will tend to channel energy in "Universal energy" rather than your own energy is focussed down the wand and through the point.