This thread should walk you through the shielding, cleansing, etc Purple's Beginner Advice (Basic Magick Energy Exercises) - #2 by Purple mostly
As for cleansing I meant more in a spiritual way (cleansing your area from lingering and negative energies etc), essentially this is “spiritual hygeine” rather than regular hygeine. It should be done before the ritual so you have an energetically clean environment to work in.
For cleansing I would recommend using this energetic audio which automates the process The Energetic Salt Cleanse - YouTube
Of course, it’d be best to do it manually but it should be sufficient for you, I do recommend working manually over relying on audios though just for the experience you’ll gain.