Word of warning, never ask a magus question unless you’re ready for a long ass answer. It’s a good question, worth some time explaining.
I use a banishing ritual loosely based on the Lesser Banishing Ritual of the Pentagram (LBRP), which is a standard in Western ritual magick. It’s used by the Rosicrucians, the Golden Dawn, and the OTO. Someone may try to convince you that it has ancient roots, but by my best guess it was used no sooner than the 19th century. You can find some good descriptions of it here, here, and here.
This is a story I tell my students often. It took me a long time to get off my ass and start using a banishing ritual. Many occultist recommend doing it every day. And by banishing ritual I mean something to clear yourself of negative influences and purify yourself, not something to exorcise specific entities. While you could use the LBRP for that I would design something suited for that particular task.
I refused to use the standard LBRP because very few resources will actually tell you what the words you are intoning means. I believe it’s vitally important for a magus to know what they are saying. When I finally did find out I discovered that one of the ancient Hebrew names for God it uses is “Adonai” translated means “My Lord”. You can make all the arguments you want, but I know that word was used to personify God as a Lord, a medieval potentate that must be served. I’ve never seen God that way. see Knowledge
Then I discovered Peter J. Carroll, and chaos magick, and finally came to the conclusion that I can use the basic form of the LBRP, but make it my own. I think it’s worth using his description of what a banishing ritual should entail.
“A well-constructed banishing ritual has the following effects. It prepares the magician more rapidly for magical concentration than any of the trance exercises alone. It enables the magician to resist obsession if problems are encountered with dream experiences or with sigils becoming conscious. It also protects the magician from any hostile occult influences which may assail him.
To develop a banishing ritual, first acquire a magical weapon — a sword, a dagger, a wand, or perhaps a large ring. The instrument should be something which is impressive to the mind and should also represent the aspirations of the magician. The advantages of hand forging one’s own instruments, or discovering them in some strange way, cannot be over-emphasized. The banishing ritual should contain the following elements as a minimum.
First, the magician describes a barrier about himself with the magical weapon. The barrier is also strongly visualized. Three dimensional figures are preferable.
Second, the magician focuses his will on a visualized image: for example, the image of the magical weapon, or his own imaginary third eye, or perhaps a ball of light inside his own
Different forms of three-dimensional barriers that the magician can create using the magical weapon. A sound concentration may additionally or alternatively be used.
Third, the barrier is reinforced with power symbols drawn with the magical weapon. The traditional five-pointed star or pentagram can be used, or the eight-pointed star of Chaos, or any other form. Words of power may also be used.
Fourth, the magician aspires to the infinite void by a brief but determined effort to stop thinking.”
So that’s it in a nutshell. I do recommend performing one everyday if you want to seriously practice magick in the Western tradition. I also believe you should come up with your own ritual based on these guidelines. I would be happy to describe mine in specifics if you want to use it generate ideas.