Understand triggered effects, deaths, and replacement bodies
Track effects one step at a time. A clear may leave new minions behind after the first ones die.
One card can cause many events
Playing a card, summoning a minion, using a Battlecry, dealing damage, and causing deaths are different events. They do not all happen at once.
An effect that reacts to a summon may work differently from one that reacts to playing a card from hand.
A board clear may kill minions that leave new bodies or deal more damage. Check the final board, not just the first wave of deaths.
Follow the steps
Read the card's current text. Ask what starts the effect. Track which minions are still there and how much board space is free.
The order cards were played can matter. The exact timing can matter too. Do not assume every effect follows a simple “left to right” or “oldest first” rule.
Reborn and Deathrattle may add another group of minions. Several waves of damage may hit those new bodies. A single wave may leave them alive.
Check unusual cases
One card's rule does not prove how every other card works. If a tricky effect decides your plan, check a current ruling. You can also test the exact cards in a friendly game.
Write down the cards, board order, and steps when something surprises you. “A new minion appeared between the damage waves” is more useful than “My clear failed.” Learn common effects in your deck first.
Related patch
See the September 28 Battlecry play fix.