Picado is the Spanish guitar technique of playing melody or single note lines. For classical guitar is also known as the rest stroke. It is called so because after your finger plucks the string, it comes to rest on the string behind it. In this way the finger pushes the string slightly downward instead of upward. The effect, if done correctly creates a stronger, louder note.
Alternate the index and middle fingers in this sequence of steps to train the fingers.