Your turn is divided into five phases, some of which have separate steps. They are:

  1. Beginning phase
    1. Untap step — untap all your cards in play.
    2. Upkeep step — You or your opponent can play instants, and card effects may happen at the beginning of your upkeep.
    3. Draw step — you draw a card.
  2. First Main Phase — In your first main phase, you can play a land, and play any spells you can afford.
  3. Combat Phase — You attack your opponent.
    1. Chance to play instants.
    2. Attackers are declared.
    3. Chance to play instants.
    4. Blockers are declared.
    5. Chance to play instants.
    6. Assign combat damage.
    7. Chance to play instants.
    8. Combat damage is dealt to creatures.
    9. Chance to play instants.
    Certain minor details have been omitted for simplicity.
  4. Second Main Phase — This is similar to the first main phase — you can play a land if you haven’t done so already, and you can play as many spells as you can afford.
  5. End Phase
    1. End of turn step — any cards with abilities that happen "at end of turn" happen now.
    2. Cleanup step — if you have more than seven cards in your hand, you discard down to seven. All damage is removed from creatures. Effects that last "until end of turn" end now.
Either player may play instants during any step except the Untap Step and the Cleanup Step.
In case of problems, email my friend (a Magic Judge) at morphling@eircom.net.