Well, this thread already has the basics covered so lets talk about some of the more interesting things you can do or things that I did not find obvious right away. In order of usefulness.
1st. The amount of data each additional item type uses scales with the size of the disk. From cursory observation, it seems that a disk with 63 item types on it will take about half the storage of the disk regardless of size. This is why pre-formatting is useful, to limit the number of items stored on disks that will have tons of each item type.
2nd. Level emitters are awesome. They are cheap, and they let you pretty easily set up operations to automatically process goods while keeping a stock on hand for other uses. (for instance, I centrifuge lava, and use a level emitter to keep a certain amount of electrum on hand before splitting the rest up into gold and silver).
3rd. Routers are awesome. They let you hook a single interface or export bus into multiple machines, or withdraw from multiple machines with a single interface. They work even better with AE than they do without, since interfaces are an inventory a router can eject to without creating a feedback loop. This lets you extract from lots of types of machines in a row and automatically eject into the network. Saves you a ton of quartz and power in input busses.
4th. XYcraft Fabricators are awesome. They treat an interface with items in it (by placing them for export) as an attached inventory. This lets you do always-on complicated auto-crafting very very quickly using only an interface and import bus (for instance, i use it to make industrial diamonds with coal from my wither farm).
5th. (links well with 4) items set to export in an interface will create crafting jobs to make the item if there are none on hand (can also do this with export busses using the craft modes). For example if you set an interface to keep flint available for the fabricator, it will use your crafting network to grind up gravel automatically if you have taught your network how to do so.
6th. You should use GT electric crafting tables for dust compression. Each electric crafting table handles up to 9 tiny dust types when in dust mode, 1 more than an export bus can output. Since partial stacks of tiny dust are useless, simply let them sit in the crafting table until you have full stacks. Much more space efficient than other options, and keeps all the partial stacks from showing up in your network, and they never clog up from partial stacks.
7th. You can use adjacent interfaces or an export bus into an interface to feed items right back into the network. An export bus in craft mode can be used with a level emitter to keep items on hand (using minium stone for instance). Or to teach the network about processing it does automatically. (for instance, if you turn all gravel into flint with an export bus on a macerator, but want the network to know that if it creates gravel with your minium stone it will get flint out in case you run out of flint).
That is all I can think of off the top of my head. Hope it helps some people to do some interesting things.
EDIT: Others covered point 1 between when I started this post and now. They also linked the storage math which I had not seen (recent addition?) which confirms my observations.