So I've been thinking about style recently.
I figure there's two kinds of statblocks.
There's the kind that goes at the end of the book where they list out all of the numbers. It needs to be narrow enough to fit in a two column format. The most important factors are readability and completeness (because some people might want an “official” set of numbers for a monster).
|AC||4 ||Int||7 / hungry|
|Atk||+4/+4 Claws (1d8)|
Defensive stuff, mental stuff, and attacky stuff all have their own sections. They're mostly listed in the order that they'll be used, too.
Movement, and Attacks each get their own line, because those are the things that are most likely to overflow. Special Abilities go last, and leave room for however many you want to tack on.
There's potentially room for more stuff on there (Strength, Treasure Hoard, # Appearing, Alignment) but I didn't include them for good reasons. Strength might be useful for a DM who is trying to figure out a grapple, but a lot of DM's have grapple/shoving systems that use HD to figure out how hard it is to grapple something, rather than Strength. Also Str is often pretty intuitive (while Int is not).
Treasure Hoard and # Appearing are usually already included in whatever module spawned this monster. Room descriptions already tell you both of those, and random encounter tables usually tell you how many are appearing.
And fuck Alignment. It's always pretty obvious. That's like listing the color of orange juice on the side of the box. (And if it's not obvious, you can just stick it down in the Special Abilities section.)
Then there's inline stat blocks. These are the ones that go in the middle of a paragraph, usually in the middle of a hex or room description. The most important factor is conciseness.
Troll: HD 6, AC 15, Claws +4/+4 (1d8), Regenerate 3, XP 800.
HD, AC, attacks, special abilities, and XP are always printed.
Saves are assumed to be 5+HD, roll under with a d20 = success.
Reaction modifiers, intelligence, movement speed, and morale are straightforward enough that the DM can set them on the fly. (e.g. Snakes run slower than a man, horses run faster.) If any of these are remarkable or non-intuitive, they will be listed.
XP might be a little bit redundant, but I personally find it a pain to tally up all of the XP after a session. It'd be nice to have a little inline number that I could just add up as a monster gets killed.