Start by browsing the coops tab above - they're set up by large, med. and small sized coops. You'll get some great ideas.
For a four season coop, build in a lot of closeable ventilation. I love my main coop and get lots of compliments on it, but I regret not having MORE ventilation. I built with winters more in mind, and now am paying the price during our HOT, HUMID summers. Wired window openings can be covered with plexiglass "windows" for winter time, so lots and lots of openings is desirable.
And if you're on this site much, you'll see tons of posts of "I wish I'd built bigger." While you think you won't need it, build as big as you can, giving the birds as much space as you can, bigger than suggested minimums. Chickens don't like snow, and most avoid walking around in it (for obvious reasons...lol), so if you get winters with snow, the extra space will be welcome...
Good luck and happy building!!