OK, so to be clear, turning the nipple clockwise as I look down on it tightens the spoke?
Still not clear. I don't know what you mean by "look down on it." Are you looking at a nipple that's on the far side of the wheel, so that you're looking past the hub at it? Clockwise would loosen in that event. Like you're looking at a nut from the bolt-head end, so turning clockwise moves the nut away from you, thus away from the bolt head, thus loosening it.
Never mind. Just think as Mike and cx advised you. It's a nut, threading onto a bolt (the spoke) in the normal right-had fashion. If you thread it on further, it shortens (tightens, pulls on) the spoke.
cdh, my truing stand has its feeler gauges up at eye level, close to me. when I adjust a nipple that's near the gauge, I'm looking "down" on the spoke "through" the rim (so to speak). In that position, clockwise tightens.
I think there was a similar discussion here about cable adjusters a while back. It's all just instinctive to me now, so I have trouble explaining it in words. Hands on, I'm confident I could make just about anybody get it in 30 seconds.