The finished mask should fit snugly on your head. The only way to get a perfect fit is to try it on a few times, adjusting different spots as needed.
Try to flatten your hair as much as possible before donning the mask so that you don't get any lumps. Some catwomen wear their hair down with the mask, too.
If you used a thin fabric that frays at the edges, use seam sealer to keep the edges from looking frazzled.
Here are some photos of Catwoman costumes to get you thinking about what style your mask can be.
(Need help? Ask in the forum.)
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