Naming Ceremony: Once a Acolyte has proven themselves worthy, they are brought before the circle of Lords to be given a name and the title Darth. Sith names cannot be repeated, there can only be one with a particular Sith name.
Tattoo:Once given their name the new Master is taken to a deep tunnel where the naming ceremony is completed. They are given a tattoo to prove their loyalty to the Sith. Getting the tattoo is a painful experience. The tattoos are always unique to the individual, though it isn't uncommon to have the symbol of the sith on tattooed onto them.
The tattoos are usually done in red or black. Red representing the murder the Sith has done while black shows the sacrifices the Sith has made.
Other colors can be used, though nothing bright, only dark colors are alright for the tattoos.
The tattoos can be complicated like
this or simple like
Darth Bane's face tattoosMore images and such can be found
here.
*Not all sith have to have tattoos. Instead of tattoos some get piercings. As long as it is a physical devotion to the sith, it will count.
*Not all sith must have a Darth name.