I had my students put a post it note in plain site that said, CHANGE FOOT! or CHANGE __________ (fill in the blank, stitch width, needle position, etc.)
Also, keep a note with your project on what you did (moved needle to 5.5 or set stitch length at 2.0) so that if you put the project away and so something else in the meantime you can have the exact same seam width you started with.