This is one of the most simple yet fundamental things you will need on your altar. Once made, you can bottle it as it has no expiry date.

You need rock salt that you only use for rituals and well, rain or spring water. After casting your circle, you take your athame and draw an invoking pentagram above the salt and see it like blue light above the salt. Now see it absorbed into the salt, leaving the salt slightly glowing. Command that the salt is now purified and empowered. Take the water and pour it into your chalice. Again, envision the blue pentagram and see it absorbed into the water and command that the water is purified and empowered. Now add some of the salt to the water. Stir with the athame. This is where the god symbol of the athame joins with the goddess symbol of the chalice and you now have holy water. You can use it for damping down static in your circle or for yourself.

The rest of the salt is already blessed so you can either use it in future holy water or you can use it to cleanse crystals with but, if you do, then you have to discard it after, as it will absorb the negativity off the crystals