A sigil is a desire or thought that a practitioner transmogrifies into a symbol that is used for his or her magical purposes. Essentially, sigils are a symbolic form of spell casting. Sigils are often used by chaotic practitioners these days and the modern idea of what a sigil is & how to make them is actually modern. It is important that we note that sigils can be traced back to Medieval times, but traces can be traced down to the stone-age and possibly further. People do say that sigils have been used ever since we've made symbols and images. We should know that how sigils were used then aren't exactly how they were used now but the context of them still remains the same. In fact, different religions and cultures had and do have their own variations of sigil magic. Some ancient practitioners used sigils to call forth spirits and those sigils were archetypes for those spirits. There are also those who call these sigils that represented spirits "seals". Another depiction of sigils is in The Lesser Key of Solomon too. Some of these traditional cultures based down their sigils to newer generations.
The modern idea of sigils being made to bring forth one's desires was actually popularized by Austin Osman Spare. It is important to note that modern day practitioners tend to like the idea of creating their own sigils and having the sigils personal to them, unlike some traditional cultures. Many practitioners believe that sharing our sigils will make it vulnerable and can get attacked.This goes back to the reference of them often being used by chaotic practitioners. Spare was a major involvement in chaos magic and the idea of magic in the modern world. It might even be best to say that his ideas related to occultism are actually deprived from symbolism and art nouveau. For those who do not remember or those who have not taken Art classes, art nouveau is the use of flowing curves and linear lines to bring forth an image (it often correlates with art deco if that helps jog your memory). The way he went about sigil magic and defining it is now called sigilization. There are some people who even claim they use sigils in divination. Another modern & common usage for sigils deals with thought-forms; however, I won't get into that.
Remember that sigil making and what you use sigils for is all up to you and is personal. This is just a standardized outline with some of my two cents. Now, let us discuss the modern creation of sigils...
Step One - What Is Our Desire & Write It Down:
We should take a moment to think about the desire we have and want to achieve. It is important to note that several practitioners do not like to get specific with their desires being written as it can mess with the construction of the symbol later on. Though, it is important that our intention is thought out as we go through this process. I tend to avoid things like "I wish for" or "my desire is" when writing down my desire because that comes across to me as relying more on faith and not trusting the sigil itself. I write down my desires as if I already have it in my life that way I know I will get it. It is almost like an intuitive situation when we know we will get something. I also avoid one or two-worded desires because I don't want my desire to come across more open than it really is despite how thought out it might be in my head. We can write our desire and sigil on anything we want or have, really.
Step Two - Reducing:
The second step to making a sigil is to simplify it, but the two ways we can do this is optional even if both are recommended. This is done by crossing out any vowels we see. The vowels include a, e, i, o, u, and sometimes y. Personally, I like to use the y because I think it looks good with the design for the most part. After we have crossed out the vowels, we can also cross out any repeated letters too. Some practitioners use punctuation and other practitioners do not so we can decide on that individually. Any letters left over will be what we use to make our sigil with.
Example (a bad desire, I guess): I have a boyfriend now-
I h a v e a b o yfr ie nd n o w- I h a v e a b o yfr ien d no w - Letters Left: HVBYFRDW
Step Three - Creating Our Sigil:
Now we are ready to draw our sigil! It is often considered that the first version of our sigil will be the most powerful, but I don't believe in that. We should make our sigils the way we feel good and comfortable with; the one that we feel "overwhelmed" by. A good friend of mine pointed out a suggestion of making sigils seem to "flow" as being a good way to make them. There is no specific way to design them so we might find it best to make it appeal to us as individuals. The letters can be in any placement we want. We can even take two or more letters and use them as one. Like, we can use an "M" to also represent a backward"W".
Step Four - Activating Our Sigil:
Activating our sigils is probably the most subjective thing aside from designing them. There are so many methods to use and make when creating a sigil. Some references say that you should burn the sigil so it can take effect or even burn it after it is done doing what it was designed for. Other practitioners even bury their sigils into the ground. One method that I made up and use is that I write my sigils on my hands or wrist and let them fade/wash away as they take effect.
We should remember that sigils are a personal and individual practice, but there is general information about them. There is no wrong or right way to create them and people continue to come up with new methods in regards to them. They are a fun thing to do, are creative in regards to Art, and they have had good reports on working more so than regular spells. I find that they are also good for helping a beginner to understand a spell too.
If you would like to get started with sigil magic then you should definitely look into it! Due to their popularity, information about them is almost really easy to find. There are plenty of YouTube videos and searches that try to explain sigils & how to make them. Here is a list of books that I've heard are helpful:
Oven Ready Chaos by Phil Hine
Basic Sigil Magic by Phillip Cooper
Practical Sigil Magic by Frater U D
Common knowledge that I have gained through practice.