SOme chords like an E are fine to strum any way you want, others like A require that you only strum the top 5 strings (i.e. missing the low, thick E string) or a D requires you to only strum the top 4 strings missing the low E and A strings.
As far as the pattern is concerned well that is dictated by the song.
My instructors page and www.studiotrax.net for all things recording.
my toons Brought to you by Dr BadGAS
my toons Brought to you by Dr BadGAS