|We are advised that best practice is to discard the machine needle after each project(!) but that seems extravagant to me, and after all, I would check the needle for snagging when working out the stitch size etc. on the next project.
When I want to keep a needle for re-use I take a fabric scrap from what I have just finished. The needle comes out of the machine and is pushed through the scrap, then into a little storage box. That way:
1: a used but re-usable needle doesn't get mixed up with brand-new
2: I have a visual reminder of how much use it's had
3: I know the needle size from the fabric without having to read those tiny figures, and don't for example try to sew a curtain with a size 70/10 meant for cotton lawn, or vice versa.
Finally, when a needle is blunt, bent or broken it goes into a safe 'sharps' container for disposal - I use old salt/pepper cannisters from the kitchen, the kind that have a hole covered by a swivel cap. It's useful for pins, hand sewing needles, craft knife blades etc.