As I had touched on in Tools Of The Trade chapter, Cauldrons are an important tool for witches and wizards. Most people only use cauldrons for one or two things- carrying things around, potions or burning things like incense, ..  all are perfect uses, .. however you can do so so so much more with cauldrons, and many differnt kinds of cauldrons.. 

I will not focus too much on potions, as there is already a chapter on various potions.. 

Cauldrons can be used for charging items to be enchanted, blessed or cursed.  Place the item in the cauldron along with any appropriate spell components- herbs, crystals, written out prayers or spells, rune stones, object links, etc.. charge each thing with intention of its purpose to assist this spell work and add its power to the spell to better focus those energies and properties.  likewise you can use a voodoo doll or poppet of someone to place in the cauldron to focus magic on them. (personally i use this method when doing absent healing magic)   if you are affecting an object in the cauldron (or person represented by a doll) then after you cast your spell and see and feel the magic working inside the cauldron put the lid on and keep in safe place- some people choose to have altars to place it on, others may choose to keep it on a bookshelf or in a closet or on a table or magical workspace..  use your intuition to figure out when the spell is over with and you can disenchant the components or items and clean out the cauldron for future use.  if you feel the spell should have a little boost then cast an energizing spell at the cauldron visualizing blazing flames under the cauldron heating up the magic within. .. 

the reasoning for keeping a lid on the cauldron is to keep all the magic brewing inside the cauldron being highly concentrated going into the item that needs to absorb that power.  when the lid is off or it doesn't have a lid the item may still be charmed but not nearly as powerfully. when the lid is off the magic rises up out into the world around you- which is perfectly useful for this next usage for cauldrons. 

Using a cauldron for spell work without a lid is just as powerful as magic with a lid- just a different type of magic- that is why it is very useful to have at least one favorite cauldron that has a lid so you can use it with or without the lid any time you want...   cauldron magic without a lid is for when you want to attract something or affect change in your life or the world around you, transformation magic  and really anything that is not specifically charging an item . Without the lid you can use this method for candle magic (preparing a magical candle to be burned for the effect of a ritual ) use a small jar candle or if you use tea light or votive put it in a glass votive holder. add around the candle any herbs or crystals, written charms object links or anything else that will add aligning power to that spell. once you cast the spell (with or without candle or whatever) you should see and feel the magic swirl inside the cauldron and rise up out.. depending on the spell, the magician themself and their own auric energy at the time how it may appear can vary. With me i've seen different colors of smoke rising up, i've seen different colors of mist or fog rolling off the top, i've seen different colors of fire, of lightning, of like a kind of lightenend smokey plasma.. of beams of light, sparks.. you oftentimes will be surprised at how your mind percieves the magic you've just cast... typically if you are surprised at how it appeared then you've been more successful because it shows you are seeing what magic has just been used in its true form- your mind has not influenced how you want it to look to you.  

you can also use cauldrons for divination and scrying. Fill a cauldron with water and gaze into it... or find a mist maker to put in it and scry from the mist.. dry ice is good substitute and excellent for scrying as well..   fire divination.. casting pebbles or runes

As i had just mentioned mist makers and cauldrons can be useful.. not just with divination but also spellwork.. if you get a misting cauldron, commonly available around All Hallows Eve, you can drop pennies into the cauldron with wishes. if the wish is for you, then breathe in the mist if it affects others or the world around you then wave or blow the mist up and away. ..  charge crystals and drop them in the cauldron so that their power may infuse the water- which turns to mist and dissipates in the air, infusing the air around it..    or put a few drops of specific essential oils into the water- working similiarly to how the crystals infuse the water and air- the oil will do the same- learn which oils are good for what. .. plus it smells good 

and the more common uses for cauldrons of course, burning incense or spell papers- carrying magical supplies or used as a catch-all, and potion making