What is the best recipe for a home-made pesticide, to keep ants and other bugs away from vegetables & plants?

Crushed eggshells in your planter will keep snails and slugs away... The shells cut them up pretty good. I've also heard used coffee grounds sprinkled about your plants is good for ants. For ant nests I've always used a large pot of boiling water poured into the nest works great. Destroys the nest and cooks them in place at the same time.