Graylady's strategy (allowing for my/your own personal opinions on 'value' of certain objects) is a great approach.
Two other exception I use:
- I typically will not fill an order that has 2 or more items requested from one factory, (same item or different items)
If a farm item takes less than 5 hours to grow, I typically treat it as a $0 value/cost item (as if it wasn't part of the order, since the cost to produce it is nearly negligible in coins. Plus harvesting it adds some small XP points as well.
Of course, my barn is not as big, so my stockpile is much smaller. Currently, barn size is 475.