Build excess residential capacity. You want to increase the chances that the elevator will take a bitizen to a level with a vacancy.
Higher skill people slightly decrease the stocking time, but more importantly, people working at their dream job double the stock at one tier, three dream-jobbers double all the stock. (Ordering times remain the same) Also, you get a Bux when you place a person in their dream job, even if you evict them right after. So you want high bitizen turnover, to increase the odds of getting the bitizens you want, with dream jobs that you can match for the bux. Don't let a person work at a job that's not their dream job unless there is another vacancy on their residential floor. A skill 2 person working their dream job is better than a skill 9 person not working their dream job.
You want to use Bux to improve your elevator immediately, at least to level 4, if not 5. A faster elevator makes the game far more pleasant to play (though it's a lot harder to make a level 5 elevator drop off a person at the desired imperial level)
Build more service levels than the others...as Han mentioned, Imperial Court is the level with the highest base amount of stock, and that's a service level. You want that to have 3 dream-jobbers, to double the amount of tier 3 stock, you want to throw upgraders at that, to increase the stock even more, so that when you throw a Big Spender at it when the level 3 stock has just been filled, you make lots of money selling lots of tier 3 stock.
If you don't have that level, throw your upgraders at whatever level has the potential to have the most level 3 stock until you get Imperial Court.
Prior to the upgrade last week, imperial assignments gave out way more money then one had to put into them, which made them worthwhile investments. That does not appear to be the case now, so I think you can just ignore them, unless one happens to pay out bux or VIPs. You need the money for your new levels.
If you want to know how to organize your death star, it doesn't much matter. I put all my residential levels at the bottom, and group the rest by type. Part of me is tempted to reorganize by the # minutes it takes to order tier 1 stock, so that Workout Center and Mos Espa Cafe will be next to each other.
The "Find the Bitizen" events will get to be more of a pain as your tower grows...consider dressing people so that you know where they work. If a bitizen isn't at work, they are at home. (Rebel spies can be on any positive level, even levels under construction)