Gray Merchant only checks devotion as its trigger resolves. You're able to minimize your losses if you can minimize the player's devotion in response to the trigger!
Author: bimmerbot
Responding to evolve by killing the creature that just entered.
If a creature that triggered Evolve is gone by the time the trigger resolves, the trigger just uses the last known information about that creature's P/T when it died. That means Doom Blade or Bile Blight will give different outcomes when responding to an Evolve trigger!
Springleaf Drum and summoning sickness.
"Summoning Sickness" only stops creatures from attacking or being tapped to activate their own abilities that include the Tap or Untap symbol. Being "sick" doesn't prevent tapping a creature to pay the cost of another ability.
Treat each other with respect, in accordance with the MTR.
Being respectful of others isn't just the right thing to do, it's also a requirement of the Magic Tournament Rules.
Drown in Sorrow vs. Mutavault.
Drown in Sorrow only affects things that are creatures at the moment it resolves. Any creatures that appear later in the turn won't be affected!
Acolyte’s Reward and changing Devotion.
Acolyte's Reward only checks your devotion to white as it resolves (not before, not after). So the amount of damage that will be prevented/dealt is locked in at that moment.
Their Bile Blight vs. your Pack Rat – Killing your own creature can be good for you.
Bile Blight needs its single target to be legal in order to resolve and do anything, so you have the chance to remove that target in response in order to save the rest of your creatures that share a name with it!
Courser of Kruphix and Sphinx’s Revelation.
When drawing multiple cards at once while playing with the top card of your library revealed, each draw is interrupted by revealing the next top card before drawing it.
The importance of shuffling (piles are not enough!)
Piles are not random, and therefore aren't actually shuffling. You must use a shuffling method that actually accomplishes randomization (side/mash shuffling, riffle shuffle).