Step 1: Gather materials. You need a small dish filled with water (this is my paint mixing dish, so that's why it's so dirty! :) ). Get some toothpicks, black and white nail polish (I used Ulta white and Wet and Wild black). You will also need some nail polish remover for cleanup.
Step 2: Make you spiderweb pattern. Drip a drip of the black polish into the water. You will see it "disappear" into the water. It's really weird! Now, add a drip of white. This paint should fizzle out a little bit but still hold it's shape. Layer/drip another black and another white on top.
Step 3: To make the spiderweb look, Take your toothpick and drag gently from the center dot outward, to look like a start of a web. You don't want to break the film formed by the polish on top of the water.
Continue to pull outward at the same spots to create your spikes. Now, take your nail of choice and gently press down on the part of the pattern you want on your nail. As you can see in the last picture, the film of polish will buckle a little bit. Press down all the way into the water, then take a toothpick and roll the excess film around your finger onto the pick to make sure it doesn't ruin your pattern. Lift out of the water.
This is what your nail will look like! Continue for each nail (layering your polish, dipping, and rolling up the excess with your pick. This pattern was used for my pinky, so I made it a little smaller to not waste the polish.
Here is a close-up of the pinky. Step 5: Clean up. This is how messy it can get (if you use the toothpick to roll-up the excess as explained above, you will be slightly less messy. I didn't obviously and this is how it turned out. So make sure you do it!)
Use your polish remover to remove all excess polish (I used Q-tips. Make sure your nails are all dry before doing this, or they can smear real bad).