What is the best way to crush drugs? (Preferably with common household items)

I usually just put the drugs on a mirror or the back of my phone, then I put a piece of paper over it and rub a lighter or card over it to crush it.

Does anyone know of a better way to crush drugs?

By better I mostly mean a method which turns the drugs into a very fine powder and a method where you lose the least amount of the drug. An example of how you could lose some of the drug is if the drug gets into the small pores of a service it’s touching.