Actions are, not all that surprisingly, the things you can do whose success or failure comes down to an "Action Check".
So, what does it cover?
Melee attacks, spell casting, finding hidden things (this is your secret door check), non magical healing, hiding and moving silently, helping or hindering another character's action check, intimidation, making camp (this kinda falls into the "why" category, but whatever), making a "touch attack" (formerly known as "hitting AC 10"), persuasion, picking pockets, terrifying someone (wouldn't this fall along the lines of intimidate?), traversing the wilderness (what, no tracking?), tripping an opponent and shooting a bow are examples.
The above come with a short paragraph with examples suggesting the stat you would use to resolve the check. I'm kinda surprised that find / remove traps and picking locks weren't listed examples, as they are certainly more prevalent in "Old School" play than "making camp".
In any case, class abilities, combat situations and situations that might otherwise fall under a general "DM Fiat" ruling get wrapped up nice and neat into the Actions that PCs can make. I've participated in conversations / discussions / rants about DM Fiat in the past, but to summarize my thoughts on it, I think it's one of the things that defines "Old School Play".
Which brings up something that I think needs to be pointed out.
Monsters & Magic is not an "emulator" of "Old School Play". You are not going to use M&M to game with the expectation of a 0e experience. This isn't a way to install Windows on your Macbook.
Instead, Monsters & Magic is more like a "translator" of sorts. You get to play your classic adventures in a "New School Environment" with minimal fuss. It's a different experience. It's closer to using Pages in an OSX environment to manipulate a Word document. Maybe not a prefect example, but it helps.
This means I need to do a 180 on my approach to M&M, which had been "how well does M&M evoke 'Old School Play' with modern play additions". Instead, I need to look at "how well does M&M translate 'Old School Adventures' to a modern play system". Two very different questions, and part of the reason for the length of time between the 2nd and 3rd parts of this review as I struggled to redefine my focus.
It's not that Monsters & Magic isn't up front with the intention of being a translator and not an emulator, but the presentation and trappings are certainly old school in nature even if the system isn't.
I'm not sure I'd still refer to it as "New Wave OSR" as I dig deeper, as the Old School is in the translation and not the play. I'm impressed with what I see so far, and as a tool to bring some classic adventuring to players on the modern "storytelling" type of RPG it seems to be on the money. The play will be different, but those coming from outside the OSR probably will never notice the difference ;)
I'll probably hit on "Effects Points" in the next part.