Rank on Dune depends on your score. The higher your score is, the more chances you get to be high ranked. Note that score isn't automatically updated. It is freshen at login, when you save your character (or by an autosave) or when you type fix. This is to prevent lag, of course. Your rank is updated automatically when the list is rebuild.
Score depends on:
better your use them will improve your score
An additional 5% bonus is awarded to playerkillers regarding to the fact that a playerkiller's life isn't always easy and considering the risks they take by becoming playerkiller.
In this scheme we try to take as many things as possible in consideration. Since quests are no longer compulsory, doing them although will improve your score.
Only people with a score of 1500 or more will be ranked. This score is generally reached at level 15-20.