Everything carries energy. It is important to 'clear' that energy out from time to time - or when we get something new/used, otherwise that energy could start effecting us or our space negatively. Fortunately cleansing is simple. Here is how I do it.
Set your crystal(s) in a bowl with some sea salt and luke warm water. Let them bathe for a few hours in the sunshine or in the moonlight. You can also choose to "smudge" them before putting them into the water. To smudge them, simply light some Sage on fire and then blow it out like you would an incense. Run each crystal through the smoke while imagining it being 'cleansed and purified' and all the negativity going 'up in smoke'.
After your crystals are cleansed, take them out of the water and set them on a towel to dry. Then place around your house or wear accordingly.
Once I removed my crystals I added some White Agate beads
to cleanse them and make a Birthing Bracelet for a customer.
Intention is EVERYTHING. The energy within Gemstones and Crystals works to it's fullest potential only when you use them with faith and intention. If you don't believe that Crystals can help you, then you probably wouldn't notice even if they did. Also, if you don't know WHAT it is you want your Crystals to do for you, then how can they work for you? Not that there is something wrong with just keeping Crystals around, this is just another way to enhance your Crystal experience.
To infuse your intention into your crystal, simply visualize your intention in your mind and heart. Let that vision swell within you as you take deep breaths. Then, when it feels like you are pouring over with this feeling, take a deep breath in use your breath and exhale it into your Crystal. Visualize and release that intention while blowing this breath into your Crystal. Then, place in your home or wear accordingly.