I agree, always start your best players. Although, I usually try and avoid certain situations with defenses. Like for example if someone has presit holmes and I have the defense they are playing. The swing in a scenario of preist goes buck is too much, as I lose and he gains, rather than him gaining and me just staying pat. In those scenarios I try and see if another favorable matchup can be exploited.
But yea, play your best players. esepcailyl in the case where YOU have the quarterback and the other guy has the receiver. the receiver has a hard time scoring withotu the qb, so your hand is always in the cookie jar.