If you've never built anything, like me, get a good pair of working gloves and a couple decent wood clamps...so many things to add here but I couldn't have built mine without those two items. Also be prepared to make lots of mistakes but they can be fixed. Make a well thought out design but be prepared to change it up if needed. And don't be too hard on yourself. My coop has been done for months now but I kinda miss building it. 
