Patches Guide to AAA Credit Rating:
Step One:
Avoid creating/joining a Government, the establishment, military, public sector, and any form of organization will undoubtedly lead to financial trouble down the road. Look at someone the wrong way, take the wrong planet, or inhabit the wrong system, and you are most likely going to war. War stimulates your manufacturing sector, but then all those shiny resources you got are getting turned into credits to fund your war effort... build more ships, blow up more ships, lose more ships. The cycle never ends.
Step Two:
Never own a planet. A planet comes with people. People are needy. They want things. Things that cost credits. Also can result in painting a target on oneself, and then you go to war. See step one for further explanation.
Step Three:
Less is more. Much like step two, never go beyond your means. Why food and cloth an army? You are just putting clothing on them and food in their bellies, only to send them off to their death (especially if they encounter angry siths). That's poor ROI.
See that shiny new big ship, with lots of cool tech? Tech breaks. Ship breaks . Costs credits to fix ship. Warranty won't cover it because it ran into a pack of angry X-wings.
Lower overhead means you don't need as many credits to cover costs.
Step Four:
Never take a side. There is always a losing side. Why turn profits from only one side, when you can turn profits from every side? Leave the fighting, shooting and blowing stuff up to others. You just handle the invoicing and collecting, and watch the credits role in!
Warning: The above steps, may help ensure a top notch credit rating; however they will just as likely ensure a shorter lifespan, so enjoy your hard earned credits while you can!
Also, on unrelated note (but to earlier posts) X-wing novels rule.