Checks for your nails

You need: Nail varnish and a tooth pick. 
This is what you do: Paint your nails as usual and, before the varnish dries, use the tooth pick to draw two lines across the nail and two lines down, to create a little checked pattern. 
Alternative: Paint your nails as usual and let them dry (!). Take a different coloured nail varnish, dip the tooth pick in it, and draw lines across and down your nail to a create a little checked pattern.
You can also try different patterns and pictures like hearts, flowers, rabbits (Credit given to Gracey Grapey for that idea)