Assuming you're blocking only for layout power distribution and not signaling, the goal would be to divide the layout based on the power draw (number of locos, lighted cars, etc) in any given section at any given time.
For example, if you had on average six locos in the engine terminal, six engines working the yard, six on the mainline, and six in staging, you could make each of those an electrical block. In other words, you have to think in terms of electrical load and not in terms of geography.
With signaling, it's a little more involved. You have to logically block the railroad based on your signaling requirements, then group the blocks based on current draw. So for example, blocks 1, 2, & 3 might be on one power district, blocks 4 & 5 on a second, blocks 6 through 10 on a third, and so forth.
As far as going from one booster or power district to another, there are two or maybe three things you need to do:
The first one is pretty obvious, and that's to make sure your track polarity matches when going from one non-reversing section to another non-reversing section.
The second is to make sure you have a heavy-gauge (same as your bus) common between ALL your boosters (it's not really a ground, even if it's often labeled as such). This is important, but often overlooked. It gives all your boosters a common (hence the name) voltage reference point.
The third is to adjust your booster's outputs to be "pretty close". This assumes they're adjustable, and especially if you've done #2, this is more of a cosmetic thing to prevent abrupt speed changes when going from booster to booster.