The most accepted system is simply using degree measurements to identify headings and the relative placements of other ships and objects in space. It seems that the measurement can be given as an angle in standard position (degrees from 0-360 going counterclockwise from east) or as an angle with a specified heading. For example, a squadron leader could direct their starfighters to follow them on a heading of 200 degrees, depress four degrees; or a flight coordinator watching the dogfight from a capital ship could direct a fighter twelve degrees west; or a different reference could be used, e.g. approaching at a forty-five degree angle to the flight path of the target. Port and starboard are also used in place of left and right or west and east. Basically, any way you can think of to express an angle will work.
Hope that helps!
~ Jacen