Once a party of player characters wanted to take a castle held by evil non player characters; Frenchmen in this example.
They tried a full frontal attack and were beaten off. So they decided to use guile and trickery to attain their goal. Out of sight of the watcher on the castle wall they constructed a large wooden rabbit. And in classic Greek style, left it outside the gate of the castle for the curious and not so bright castle guardians to bring it into the castle.
Once inside the castle the player characters would leap out and take the castle by storm!
Only problem: they were not only not in the castle but not inside the rabbit.
This caused some hard feelings towards the player character who thought up the plan but forgot to tell everyone to get in the wooden rabbit so they could then surprise the garrison. Understandable and mostly a problem with sequencing.
I can’t tell you how many times an adventure session goes something just like this. It’s not always a life or death situation for a player character or a party but it is usually something that will either win the day or a precaution the player forgot to do BEFORE starting out on their latest endeavor for the day.
DM: The campfire burns down and the human player character on watch notices he cannot see as far into the darkness as he could a minute ago.
Player: I throw more wood on the fire.
DM: When did you gather wood for a fire?
Player: You know every time we camp I always cut at least a cord of wood and have it stacked ready on hand to add to the fire.
DM: Funny, this is the first I’ve heard of it….
DM: Okay, the sun is rising and the party begins to stir. Tell me how you will all start your day.
Player: I get up, eat some rations, drink some water, and pack up my gear. When everyone is ready to go I fall into my spot in the marching order and we go forth.
DM: Up ahead you see a group of surly looking non player character types. They have an assortment of weapons and look enviously at the display of your player character wealth.
Player: I prepare to cast a spell while the player in charge of the party goes to…
DM: The surly looking non player characters are attacking! It’s an ambush!
Player: On my initiative I cast Sleep on the largest group.
DM: A thrown knife (dice rolling) hits you in the chest for three points of damage.
Player: What AC did it hit? Mine is 18.
DM: 18? Your sheet says 14.
Player: But I had cast Mage Armor on myself when we first saw the people up ahead.
DM: You never told me that….
Player: Well you know I always prepare…