Want fireworks on your fingernails for the 4th? Start by painting your nails in a base coat of dark color, like blue, or red. I really like dark blue, because it keeps with the patriotic theme of the holiday, but also suggests a night sky behind the fireworks.
Once the polish is dry, add a small drop of white, and a slightly smaller drop of red (or blue, if your background color is red), on top of that. The trick is to keep the drops fairly small.
Let them dry a few seconds, until they start to get tacky, or sort of on the dry side of tacky, and then use a toothpick to spread them out from the center, in bursting spokes of color.
Let the polish dry completely, and finish off with a clear coat to smooth things out and add some shine.