I fish 16's and 18's. Mainly 18's. I tied up a couple of hundred (all together) in black, red, blue, purple, rusty, and olive. I always fish them under an indicator. I usually fish them very close to bottom, but not always. If I have fish take it at the end of a drift when the current pushed the midge upwards, I reduce the distance from indicator to fly.
I sling the fly upstream and drift as close to dead drift as I can get it. I set the hook anytime the indicator acts the least bit odd.