When opening Launchpad I've noticed that every page has different amount of applications laid out. Also, they doesn't seem to be ordered by any criteria (name, usage frequency or size). What are the sorting parameters for applications in Launchpad?
On a clean install, the core Mac OS X apps are originally ordered alphabetically. Newly installed apps will be appended at the back on an empty spot starting with page 2 (they will never be appended on page 1, even if there is room available, but you can ofcourse drag them there).
Apps can then be arranged manually, and they should remain in the order you sort them. However, I have noticed quite some buggy behaviors, mainly apps changing position after a reboot, and MAS updates pushing apps of the page.
I hope these will get ironed out in a coming update.
I'm not sure there is a fixed order. When I first started LP, they were in alphabetical order. I moved some around, combined some together, moved some to page 2 and vice versa. That new order has stuck over many shutdown and startups, even through the SU.
When I add a new app, it shows up on page 2. I move it to page 1 and it stays there. It can be tricky to get them exactly where you want, as each time you move one, another moves as well. It's kind of like trying to solve 2 Rubik's Cubes at once.
Hope this helps, even though it is just my experience and not a hard fast rule.