Firstly i would suggest cleansing your amulets,you can do this by passing them through the smoke of white sage incense or a smudge stick,this will get rid of any unwanted negative energies.
Another way would be to add some sea salt to a bowl of water and dunk your amulets in it a few times(not if it's made of wood)never place your amulet in the salt water for more than a few minutes salt water can damage some stones.
Charging your amulets.
On the full moon preferably a friday meditate while burning some incense that represents your wishes and desires, make sure you are holding your amulet while doing so.
While meditating visualize/imagine the energies that you wish to place in your amulet flowing through your body and being channeled into the amulet.
If your amulet is for ritual use take your amulet in your hands (maybe say a prayer to your deity) and and place it on your altar as an offering each day, used in rituals they are symbols to amplify your energies, i would suggest cleasing them after ritual use again if they are to be worn around your neck, you can also place them in a velvet bag with the herbs that represent your desires/wishes and carry them on your person.