I have a little plastic pot that all the sewing needle case/packets (ie, those plastic things they come in) go into for tidiness. When I use a needle the case/packet it came out of is stored horizontally on top of all the other ones. If, when I'm done, the needle still has some life in it, it is returned to the case/packet but facing the other way, ie, flat face out (or domed, whichever is the norm for the others). I start at the left side of the pack and work rightwards. That way, I know which have been used. If the next job is a quick repair, say, I'll reuse the old needle, but if it's a big project I'll start with a new one and only reuse the old one if the newer one pegs out before I'm finished (or I break it!).