Most of the time you will not be playing all six strings at once, unless you are strumming chords. Playing notes and melodies requires picking one string at a time. Select one string - it doesn't matter which one, and play a series of downstrokes and upstrokes on the one string until it feels natural to you. Use the swiveling motion mentioned above to go from downstrokes to upstrokes. If you drop the pick every once it a while, don't worry about it. Play the repeated notes as slow or fast as you like, but make sure the rhythm and loudness is even between down and upstrokes.