Do not jump up and scream, "LET'S RUN TO THE POTTY!" when you notice the that trainee has "the look" on his face. You will scare him out of going poop and have a constipation problem on your hands.
Always have rewards on hand when potty training. Apparently, two-year-old trainees do not understand the IOU concept. Example: "If you go poop in the potty mommy will owe you a treat!" Trainee: "Where's the treat mommy?" Me: "At the store. If you go poop in the potty mommy will go to the store later and buy you a treat." Trainee: "Where's the treat? I wanna see it? I no wanna go poop in da potty."
Put a tarp over all carpeted areas in the house and over all couches. Clean up will be much easier this way.
Do not have a one-year-old running around while potty training a 2 year old. The one-year old will stick their hands in the toilet, run wild with the toilet paper, and steal the trainee's toys which in turn distracts the trainee from the task at hand and makes potty training impossible.
When potty training do not buy underwear that are too big for your kid. If the underwear are too big and the trainee poops in them, the poop will roll out of the underwear and be considered M.I.A. until you later find the missing poop nugget on the dining room floor in the midst of the toys.