I also use blue painter's tape. I write the size needle I am presently using and stick it on my machine where I can see it. I also put my used needles on a piece of paper and store them in my sewing drawer with their size next to each used needle. I don't throw away a needle unless they are dull. You can tell when they start making a clunking sound as they go through the fabric or the thread frays. A tip I found is that you dull your needles fast when you sew over pins.