Ombre Nails - hit of this year. You can do it in 2 different styles.
1st one is - that you will color each of your nail on different shade of same color. Here are some examples. !!! (Be sure, that the colors matches together otherwise it would look like if you were trying 5 different colors in shop with nail polishes.)The 2nd one is about to shade one color into second color. Mostly are used really contrasting colors.
And how to do it? Just varnish your nails on black (or other color you've chose) then put little of the second nail polish on edges of your nails and before it becomes dry spread it with transparend nail polish. Done! :D