I don't have many step by step pics for this so you'll have to use your skills to fill in the gaps.
I cut 2x4s with angles to make three sets of rafters and attached them with three inch screws. I screwed down some old cabinet wood across the rafters to make the roof, leaving a little 4" hole near the center peak for a cupola. Then I shingled the roof leaving the center peak hole open.
The cupola is made like a little bird house that sits over the vent hole. Use a hole saw to make holes in it's sides and staple window screen on the inside to keep out the critters. Attach it with 3" screws.
This helps meet rule #2.
Dry with good ventilation.