One turn, phase by phase

A turn is a fixed sequence of phases, and learning them once makes the rest of the rules easier to place. The phases are rigid, but the actions inside them can be done in any order unless stated otherwise (rule 303). The Turn Player is the player taking the current turn (rule 304).

Worked example, one turn. You are the Turn Player. In the Awaken Phase you ready everything you can (rule 315.1.b). In the Beginning Phase the Scoring Step makes you Hold every battlefield you control (rule 315.2.b.2), so a Grove of the God-Willow you hold draws you a card now. A card such as Dusk Rose Lab acts at the start of the Beginning Phase, before scoring, in the Beginning Step (rule 315.2.a.1). In the Channel Phase you channel 2 runes, or as many as the Rune Deck has (rule 315.3.b and rule 315.3.b.1). In the Draw Phase you draw 1, burning out first if your Main Deck is empty and then still drawing (rule 315.4.b, rule 315.4.b.1 and rule 315.4.b.2). In the Main Phase, which has no defined structure, you take Discretionary Actions and only you may play spells or activate abilities (rule 316.5 and rule 316.5.b). When you have no more Discretionary Actions you wish to take, you must indicate that you are ending your turn, which ends the Main Phase and begins the Ending Phase (rule 316.9, rule 316.9.a and rule 316.9.b). Its Expiration Step heals all units, ends every "this turn" effect at once, such as Discipline's +2 Might, and empties the Rune Pools (rule 317.2.b, rule 317.2.c and rule 317.2.d). Then the next player with a turn queued becomes the Turn Player (rule 317.3).

How phases end. In the Awaken, Beginning, Channel and Draw Phases the next phase or step simply begins when the tasks are done: with nothing on the chain and nothing more the Turn Player can or will do, the phase or step ends (rule 305). The Main Phase is the one where the Turn Player chooses what to do, so it ends only when they indicate that they are ending their turn (rule 316.9). The opponent has nothing to agree to, because only the Turn Player can act in a Neutral Open State (rule 316.5.b).

Rune Pools. Each player's Rune Pool also empties when the Main Phase begins, so unspent Energy and Power do not carry over (rule 316.3).

Common mistake. "The Main Phase ends when I run out of things to do." It ends only when the Turn Player indicates that they are ending their turn (rule 316.9).