Might be a bit of an odd one this, but I really struggle to look anywhere but my feet/pedalboard during indoor gigs. I've played in front of 10,000+ and found this easy compared to playing to 50 in a pub. Outdoor gigs usually require sunglasses so no issues there.
What do you guys do? Stare at the back wall? The ceiling? Or do you single-out one person and look at them?