A wise neighbor once told me: "Never plant more lawn, than your wife can mow". Words to live by.
Try and plan your coop and run so you can sub-divide it. You may want to seperate your different breeds for mating, or keep young birds seperated from the adults. I built one of my coops with three doors to the run, so it could be split up later.
1) make sure you insulate enough and then insulate more just to be on the safe side
2) have some sort of heat source so that the water and poop dont freeze so you can clean the coop during the winter
3) make the side walls of the nests taller so they reach the top of the "lid" for the nests cause the chickens like to sit on there and poop on the eggs
4) for the people door, at the bottom make it so that you have to step over a "lip" so that the chickens cant kick their bedding out the people door during egg collection and daily chores
guess what my spring/summer building project is..... new coop (o silly me...did I say I was building the coop?....sorry DH is building me a new coop he just doesn't know yet...shhhhhhh!)
build it appropriate to your climate. don't take all the advice you read here at pure face value as a good design in Minnesota may not work well in Hawaii.
think about daily chores when designing... ease of reaching heavy food and water buckets, how to deal with chicken crap, getting eggs without going into the coop, etc.
Make it so you can collect eggs, clean poop board, fill food and water without stepping in if possible--then you don't have to worry about some nice fresh poo on your shoe.
Windows so you can work inside, and spy on the chicks at night with a flashlight if necessary.
A nice place to sit that doesn't get poopy--still trying to figure out that one!
Linoleum on the floor-did anyone mention that?
I really like the idea of creating some sort of brooder/hospital/separation area ability, possibly with another entrance to a separate run.
Community nest box, heck with their pickiness! Accessible from outside of course...
In calculating your coop size, do NOT count on the idea that the chickens will use an uncovered, outside run (or be willing to free range) in the snowy winter.
Chickens will peck foam insulation. Yes, you do need interior walls (preferably not sheet rock which is susceptible to moisture).
Chickens will somehow manage to splatter poop just about everywhere.
It is very handy to have your waterer in a location where poop splattering is minimized. My waterer is at the end of a narrow "shelf" - they just go up there to drink.
Plan out where you will keep supplies for the coop:
food, treats, poop bucket, pine shavings, cleaning tools (dustpan, old car snow brush, kitty litter scoop, broom), stall dry, DE, chicken care items like petroleum jelly, grit, oyster shell.