The things you need:
- black stockings (I buy mine at any store, as long as they are black and cheap, in a size L/XL because I am tall)
- Seam ripper: can be found at craft stores, sewing stores, bigger stores that have sewing supplies, or on ebay for about 1-2€
There are also methods using scissors, a knife, just ripping them with your hands, ... but I prefer this one.
Step 1: put on the stockings,
Step 2: take you seam ripper
Step 3: start creating holes where you want them by pulling the stocking away from your legg
Since a seam ripper is a rather precise tool, you can make small holes, big holes and even patterns (of you would want a skull shape etc).
I suggest doing one side first, then taking them off and putting them back on so that you have holes all over them.
You can also change them into sleeves, this you do by cutting open the crotch area, the feet and simple put it on like you would with any top.
I hope this helped you out, and if you want to see other small goth inclined tutorials, be sure to leave in the comment section what you would like me to explain.