In medieval astrology there is something that is named “Almuten Figuris” and also “Lot of Hyleg” or “Part of Hyleg” (and what is interesting it should not be confused with Hyleg). Almuten Figuris it is a planet that have a highest dignity in our chart, and it is considered our guardian angel nature, and have a purpose to guide us in our life so we fulfill it. It is considered one of the strongest factor in chart, sometimes stronger than all other planets. Part of Hyleg it is a specific point in our chart that is calculated using other factors in our astrology chart. It is the point that, well, point out the sense and purpose of our life 
So it have same job as our Almuten Figuris.
If you want to know yours, you will need some astrology program, or web side first. One webside what I found that provide almuten figuris planet (and many more stuff) is Astrofox, and it is free to use. You will need your date of birth, location and hour of birth. When you will have a chart take the angle and sign where are these: Your Sun, Moon, Ascendant and Part(lot) of Fortune. Next you will need to find your Syzygy, and it is last New or Full Moon before your birth, and take the angle and sign where it have happened.
Interesting thing is that All of these are used to calculate your part of Hyleg. So you see where it is going. Now, you took those angles and try to assign proper hebrev letter for each. How? There are few methods, so I give those i know. And here are the tables.
This up one is from medieval astrology guide webside, they have also great stuff about astrology talismans creation, not only planetary, but also fixed stars and moon mansions.
Another methods:
Use this table, unfortunately i didn’t remember where i found it, and even the google graphic search didn’t provide the results 
It source is form Cornelius Agrippa. So how to use it? Agrippa didn’t describe specifically how to use it. So you can: Take the sign where the each factor (Sun. Moon, etc.) is located. Count the letters starting from up and stop at the number of angle. Like if for eg. your moon is in 5* angle in Leo, so you count down till fifth letter, and this is it. When angle of factor is higher that 22* like 25 or so, start counting from up again, but start it from 23.
Or, you can use the table that I made for this, I divided zodiac sign into 22 pieces and assigned angles for each:
Now take the letters that you have assigned for each factor and put in such order:
If you were born at day: Sun, Moon, Ascendant, Part of Fortune, Syzygy
If born at night: Moon, Sun, Ascendant, Part of Fortune, Syzygy
At the end of name add El. And here you have it, if you use all methods you should have, like 3 names.
Which one is correct? Is it reliable?
Christopher Warnock wrote on his blog that he made an astrology chart for some magician, and provide him also his Almuten Figuris name. This magician evoked his guardian angel, and, his name was very similar with AF name, but that angel also stated that it is one of his many names. So probably all 3 names are correct, but each one gives possibility to work with different aspect of our guardian angel.
You can use it, and evoke it. I personally tried one of my names before sleep few times, and had dreams that were way different in feeling, and in the way they roll than usual, much much deeper and as if they were more stretched outside of me but also reached deeper inside.
Have fun 