try to find a reference that's a close to what you have in mind as possible. Usually, black leather will have grey, blue, or purplish highlights, but it depends on the type of leather, the lighting, if you want to stylize it, etc. Also, the "black" is almost never actually black.
For achieving the texture, be creative. You could use a piece of Scotchbite pad to spray through (probably pull it apart a bit to loosen it up first), try some erasing techniques, or scratching. Try using different grades of sandpaper to "cut" the highlights in. Try stippling. It's all fair game. Just look carefully at the texture and grain of the leather, and try to figure out how you can best match it.