I've lived through a few renovations back home, but my father has always been pretty hesitant to let his young son help out. I don't blame him honestly because time was always at a premium and having to go back and re-do things would of just added additional stress to an already hectic time.
Currently I know a few things handy. I'm confident that I can put boards together and make something of a wall that would stand. I've built bed frames, desks, coffee tables, and even a pantry before that all served their purposes. Best thing I could do right now is invest in a metal square however. Ninety-degree angles and hinges are the bane of my existence.