Every character has some basic skill requirements, skills they have learned in basic training, if not before. They must spend at least one skill point in each, to represent the most basic level of competency. You must have at least a d4 in:
Your specialty will have other required skills to represent that additional training.
In addition, to represent the extra training officers receive, characters beginning play as Officers or NCOs must take the Rank edge as well as the required skills for basic training and their specialty.