Wash on hot with detergent, drying in between. After each dry, test them by putting a drop of water on them. If it absorbs instantly, they're ready. If it beads up at all, they're not. If you have any questions on whether it absorbed instantly or not, it probably didn't. Boiling works too, and is probably less water/energy intensive overall, but I've never tried that so I don't know how long you need to boil them. It took something like 3 or 4 cycles for mine to be ready, but it's been several years so I can't remember entirely, and depends somewhat on the brand.