Cerridwen Greenleaf, author of The Magic of Crystals & Gems, has a few words of wisdom on how to correctly charge your crystals, take a look!

The first thing you need to do with a crystal is charge it, which means syncing it up with your personal frequency and vibrations. You’re placing your desires and wishes into the vessel of the crystal. The crystal’s inherent energies will come into play with your personal power, and your intentions can be manifested, or made real, through the crystal.
The very first step in this process, however, is the dedication of the crystal toward the greater good of all beings. An essential part of this process is the cleansing of the crystal in order to purify its energy. Although this is a straight-forward task, it is of supreme importance for your use of the crystal down the road. If a gem or stone is not as effective as you had hoped, the problem could stem from the initial dedication. Think of this primary step as the honing and direction of the intention. Here is how: simply hold the crystal in the palm of your right hand, and in your mind picture a glow of light surrounding the stone.
When the rock is completely enveloped by light in your mind’s eye, state out loud, “This crystal is only for exacting good of the highest order. In this stone of the earth, there is only love and light.” I like to leave the crystal out in the light of the natural rays of the sun and the moon for a twenty- four-hour period for the maximum dedication of light and love from the universe and the heavens above as part of the purification process. But, if time is of the essence, you can move right on to step number two, charging the crystal itself.
All stones possess natural energies of their very own. You want to merge your energies with those of your crystals so that the crystals will be in sync with your vibratory channel. Remain mindful of the great power your stones have and you will be in a good position to work with it. Consider carefully what kind of energy you want to place into your crystal. Take a stone that has been cleansed by sitting in a bowl of sea salt overnight and in the light of the sun for a day. Sit in a comfortable position and hold the crystal in your right hand. Focus on the energy you desire your crystal to hold and project it into the stone. Bear in mind, the use of crystal magic should not be used solely for your purposes, but also for the greater good. Please make sure you’re projecting positive energy and not anger or hatred. You should ask aloud for your crystal to work together with you for the highest good. You are doing creative visualization here, so keep concentrating until you can see and feel the energy flowing into the stone. You will feel when the charging, or programming, is complete; your intuition will tell you.
While it is not the best-case scenario, you can charge a stone for someone else. For example, if you have a friend who is very ill and halfway around the world, you could charge the crystal with positive, healing energy and send it to your friend to help them. Ask the crystal to work for the highest good of this person and then release that crystal to them.
The magic of crystals and gems
Unlocking the Supernatural Power of Stones (Healing Gemstones and Crystals)
Practice Practical Magic: Did you know that wearing an amulet of green jade on an interview will help get the job? Have you heard that an amethyst ring can help break bad habits and even encourage sobriety? Anyone looking for love can place two pink quartz crystals in the bedroom; you’ll not be alone for long! These are just a few of the hundreds of secrets shared in The Magic of Crystals and Gems. Semi-precious stones and gems have long been known for their magic as well as their beauty. In this book of charms, readers learn everything there is to know about the powers of crystals from birthstone magic to gem divination to jewelry spells. This is a fun, entertaining, and enlightening book that will appeal to everyone who’s ever worn a birthstone, kissed the ring of a lover for luck, or bought a crystal for good energy.