How do you guys remember the weights of your spinnerbaits? If you take a sharpie and write it on a blade will it stay on?

I always just know the couple of weights that I buy and can tell by look and feel.

If you use them enough you can just tell. Also, the blades themselves are roughly the same size on the same size heads and you're not generally going to have 15 different size heads. It'll be more like 2-4 and they'll all be distinctively different.

I have a lot of spinners every color in every size in a few different heads.  i have them at my house labeled planos for 1 oz down. each oz has its own plano but when i take them out for a day on the water.i put them in a cd  wallet kind of in order but you can tell the difference. after a while

I do it with my crankbaits,and havent had any probems yet. I use a fine tip sharpie.

I label the slots in the spinnerbait box.

Sharpie typically won't write permanately on metal.  If you have them stored in a Plano type container designed for spinnerbaits you could label that if you put them back in the same slots you removed them from.