Step 1: Pick and wash your basil leaves
For this Instructable I used the entire top half of 4 basil plants, but you can use as much or as little as you want.
Put all the leaves and stems in a clean sink and let them soak for a few minutes. I don't use any pesticides on my plants but there are still usually little bugs on the leaves, dirt, and the occasional spider web you don't particularly want in your dinner ;)
Swish 'em round with your hand a few times for good measure.