Before you build your coop, know what you want it to do. Are you going to feed and water in it year round? Are nest boxes inside or elsewhere? With your climate, are they going to free range every day so they will hardly ever be in the coop, just to roost and lay or will they spend a lot of time there? Are you going to hatch with broody hens?
Make it convenient for you. If you are going inside, give yourself room to work.
Have a plan to handle the poop. Not just cleaning, but what are you going to do with it. If relevant, make your door big enough to get a wheelbarrow in.
Assure the floor drains.
If you are watering inside, try to arrange so spilled water does not soak the litter.
I like having a way to enter the coop without going through the run. Most runs can get pretty muddy or you may be able to avoid stepping in pop.
Have a dry storage area for litter and food.
If you have chickens you have chicken feed. If you have chicken feed, you have or will have mice and maybe rats. Plan for a safe vermin control plan.
Read Pat's ventilation page.
https://www.backyardchickens.com/web/viewblog.php?id=1642-VENTILATION
Have a chicken prison that keeps the chicken next to the flock to reduce pecking order issues. You may use it to break up a broody, isolate an injured chicken, introduce a new chicken to the flock, or who knows what else. It needs its own food and water, weather and predator protection.
Adopt the ideas you get from here and other sources to your unique circumstances. What you need will depend on your climate, size and makeup of your flock, rural or urban, purpose of your flock (dual purpose, eggs, meat, show, pets, breeding, just enjoying their silly antics, etc), and who knows what else that makes your situation unique. There are good reasons for doors to swing in. There are good reasons for doors to swing out. Which works for you?
Contribute to this forum with your lessons learned, whether success or failure. We all need to learn more.