I took up chicken coops as a hobby, I'm a wood hack. My passion for it doesn't equal my ability at all! So this is what I've learned so far for me..
1) Decking screws with a star/square head are your friend in all sizes. You'll mess up..just unscrew it.
2) Keep it simple, they're chickens and its not a piano so relax and enjoy the thrill of the build!
3)Build bigger than you think
4)Chickens and chicken accessories at the end are not cheap, it adds up.
5)There is a plethora of free material out in the world..use it!
6)Add windows..makes it so much easier to check in on them without disturbing their roosting.
7)A coop you see may look cute like a fuzzy hybrid puppy kitten..that doesn't mean it works well or is good for your flock. So do your research, ask a lot of questions and always remember to be a 'student'.
8)PVC roofing panels are your friend, and they are affordable.
9)If it isn't straight, level and square..just stop building and make sure it is. You'll keep on paying over and over again for that.
10) The very most importanist' thing on my list...HAVE FUN, enjoy it, learn something new, be creative once you get a good foundation and structure add some herb or flower boxes, some hand painted signs with your chickens names on it. It doesn't have to be perfect to someone else, it only has to be perfect for you!