These days I like to put a piece of masking tape (think painting a house) on the front of the machine with the info for the needle written on it. It comes off easily and is typically safe for paint or baked on finishes.
Edited to add: If I am sewing and have specific changes to sew my current project, like where to move the needle to and which stitch length I am using, I use another piece to tape so I don't have to invent the wheel every time I sit down to sew.