My brothers and I built one 25' high from small poplars and my dad's tarps when we were kids. My dad was not happy.
I saw one in a magazine built with simple twig poles, set in a circle and tied together at the top. Then planted with a runner bean. I plan to do one for my grandchildren next year. I am going to use scarlet runner bean, because of the pretty blooms. It was in the May issue of BHG, I think.

Good Luck!

Grace, here's one site that may work for you. One of the pattern companies also have one, but I'm not at home and don't have that info in front of me...if this one doesn't do it for you, I'll be home late Thurs and can send you the info then if you want.

Here is a link that might be useful: http://www.hgtv.com/hgtv/cr_kid_crafts/article/0%2C%2CHGTV_3256_1382585%2C00.html

Thanks everyone I got a couple great sets of directions. I bought supplies today will post a picture when I get one finished... grace