Formal:
* Je m'en vais. (This is the most common and neutral way to say it.)
* Je pars. (This is also a good choice, and is slightly more emphatic.)
Informal:
* Je file. (This is more casual and can be used with friends or family.)
* Je dégage. (This is very informal and can be used with close friends, but it can also be considered slang.)
* Je me casse. (This is very slangy and can be considered rude.)
Adding context:
You can add context to your departure by using a preposition like "de" or "pour":
* Je pars de chez moi. (I am leaving from my house.)
* Je m'en vais pour le travail. (I am leaving for work.)
* Je file à la plage. (I'm leaving for the beach.)
Saying goodbye:
* Au revoir. (Goodbye)
* À plus tard. (See you later)
* Salut. (Bye)
* Bonne journée. (Have a good day)
Choose the expression that best suits the situation and your relationship with the person you are speaking to.