This is one of my favorite ways to do my toes. All you do is paint your toes white, which you will probably want to do more than one coat so it wont be streaky. Then when it is totally dry; use scotch tape to make a diagonal line. To get the best results use tape that is cloudy in appearance and not completely clear. The clear stuff seems to stick more. Then just paint the top black. I peel the tape away when the black is still wet. Then you are left with a nice diagonal.