We have a barn that we use for the chickens. It's continually changing. I do agree with all your input though.
- Figure out how many chickens you want to keep in coop. Multiply by 3. That's how you figure out space (in my case, multiply by 50).
 
- It comes in handy to have a divider in your coop to separate injured or broody hens.
 
- Nesting boxes should have something slanted to prevent roosting (even if they are lower than the roosts!)
 
- Lots and lots of ventilation.
 
- Something that goes in front of door to keep shavings in.
 
That's all I got. 
		
		
	
	
Here is my coop for reference..
They still roost on those darn makeshift nesting boxes. We plan on building a huge set of them eventually, but this is all we have for now. I have to kick a few off at lights out 
Also, tiered perches work great. I have more roosts then needed, which is also a plus. There is less fighting that way.