Headroom? Temperature?

I have been wanting to homebrew for a while now and a couple nights ago finally bought some starter equipment on bezosdotcom. I put together something out of what I had on hand, grapes, blueberries and honey. My water came from my birkey filter. I thought I gave it enough headspace and then tied down the bung and airlock but it overflowed quite a bit. Did I do something wrong? It seems fine now but hope for my first batch to come out decent.