After cutting them out, (I found the most success with small, embroidery scissors) I used
Krylon Easy-Tack Repositionable
I taped my newsprint to the wall and drew a tree. I had a 10-year-old tell me the secret to drawing trees was to keep making V's, so I used his method. After it was drawn I got out my brown paint and put some paint on the trunk. Next I put the leaves on the tree, started it off with a couple of things I was thankful for and invited (okay, coerced) my family to write on some leaves. My sister and I stayed with it until we got all the leaves filled in.