How do I choose wire size in relation to branch size

I use the thinnest wire that will hold the branch in place. That is totally different for different species. I look and feel the branch to make a desicion. Still a beginner so it does not get perfect every time. I guess that is a part of the process called learning:)

Br
Magnus

Bend a piece of wire against a branch. If the wire bends, then the wire is too thin. If the branch bends, then the wire is perfect.