Therefore, the Arizal says, "When a person is born and his father and mother give him his name...the Holy One puts into their mouth the particular name required for that soul".¹

B. Since a Jewish name functions as a spiritual conduit, channeling spiritual energy from G-d into the soul and body, critically ill individuals are sometimes given an additional Hebrew name, which serves as a spiritual bypass operation funneling fresh spirituality around their existing name and into their bodies. With the influx of spirituality, the body is given renewed vigor to heal itself.

C. Jewish names also serve many practical functions. A person is called up to the Torah by his (and his father's) Jewish name. All religious marriage and divorce documents must contain the Jewish names of the husband and wife. When a person is ill, prayers are especially helpful if they are said using the patient's (and his/her mother's) Jewish name. Even after a person passes on, the Jewish name plays an important role -- it is mentioned during every Yizkor service. 

Your Hebrew name functions as a spiritual conduit, channeling spiritual energy from G-d into your soul and your body

1. Beyond your Choice

Usually, your Hebrew name is applied to you at birth or not long thereafter, selected by your doting parents who name you after a dear departed loved one, usually an ancestor. Or, if they don't have anyone to memorialize, you just might end up with a Hebrew name of their own preference. Either way, Jewish boys are named at their Brit, and girls at a Torah reading shortly after their birth, so you can't really choose your own name, unless you were not given one until adulthood.

2. Within your Choice

If you were not given a Hebrew name until adulthood, namely, your parents didn't give you a brit (if you're a boy) or didn't name you at a Torah reading (if you're a girl), you can select any Hebrew name that tickles your fancy. Usually, though, it will be something phonetically similar to your English name: if your name is Bernie, you'll likely end up with Baruch or something starting with "B". See also What is the Jewish name equivalent of...?

3. Conversion Options

A third Hebrew name alternative is when a non-Jew converts to Judaism. The convert may choose any Hebrew name, but, like adult described above, it will usually be something phonetically similar to the existing name: John might become Yonatan (Hebrew for Jonathan), Mary might become Miriam. Many converts to Judaism choose the names of the very first Jews -- males naming themselves after Abraham and females after Sarah. Other female converts chose the name Ruth, after the woman who left her Moabite royal family to cleave to Judaism. Her journey from "riches to rags" earned her the right to be the matriarch of the Davidic royal family, indeed, the grandmother of the Moshiach.