You gain maneuvers and stances associated with your class. Your Initiator Level was like a Caster Level and was on a 1:1 ratio with Martial Adept classes: Crusader, Swordsage, Warblade. Other classes's who had maneuvers via Martial Study feat had a 2:1 ratio (ie every two character levels = 1 Initiator level) which stacked with Martial Adept classes. For example, a Fighter 4/ Warblade 3 had an Iniatiator level 5th (2 from Fighter, 3 from warblade).
To initiate a maneuver was much like casting a spell, often requiring a standard attack action or a skill check or something similar. They were one-shot attacks that resolved in 1 turn. In addition to maneuvers known, you could ready only so many based on your class. You could never ready the same maneuver twice.
Unless otherwise mentioned, all maneuvers are Supernatural abilities and not subject to Spell Resistance. Stances are activated with a swift action and are always active unless you turn it off with another swift action.
I believe that all maneuvers were Extraordinary abilities, unless specified otherwise. The Supernatural ones tended to come from one of two specific schools (Desert Wind and Shadow Hand).
Aside from other factors (pre-requisites, class, etc.), access to maneuvers depended upon the initiator level. It worked similarly to a prepared full spellcaster's access to spells: for example, one had to be initiator level 5 or higher to get a level 3 maneuver.
And the whole thing required some common sense to adjudicate, or people would invent infinite loops of actions.
....I believe that all maneuvers were Extraordinary abilities, unless specified otherwise......
This is correct.
I will also add that without a copy of the book it won't be possible to run the classes since you need to read the specific maneuver to know how it works. Some are immediate actions, some standard, and so on.
doh, that what I get for not reading the books when I post. Yes, Extra-ordinary abilities unless specifically says other wise. So they also work in Anti-Magic zones and the like.