Best advice I've heard on this topic, and I forget who said it, "play lots of correspondence games with opening book allowed." Make it possible to play through variations as much as possible.
I feel your pain on this topic, myself. My time in tournaments was always made less fun by those genius kids who could memorize entire opening lines. I could hold my own in middle and end-games, but those guys always beat me.
So, here's my dilemma:
I've played chess for a very long time. My skill level (at least with the effort I've placed on learning) has settled out in the low Class C level (1400+). Over the years, I've played many different openings and built several repertoires, some of which I enjoyed playing, others were less fun. The heart of my dilemma is this: I have never had a very good memory, and with age even that memory seems weaker than it used to be. So, I have gradually resorted to choosing opening systems with as few forcing lines as possible (e.g., Nimzo-Larsen, Colle, KIA, Owens/English, etc.). While these openings allow me to concentrate more on ideas and less on lines, collectively they do not bring the excitement inherent in the more swashbuckling openings (KG and other forcing 1.e4 lines, Open Sicilian, etc.). Additionally, opponents more easily prepare for my repertoire lines which are not near as rich in plans as QG or Ruy Lopez, or Sicilian Defense.
My suspicion is that there is no solution to this "prisoner's dilemma," but I am open to suggestions that don't involve quitting my job to devote my life to chess or paying $5000 for years of professional lessons.
Throw me a lifeline, someone. I'd be grateful for any (non-flippant) advice.