I wave at
everyone, usually first, unless I'm in a situation where I'm needing my hand on the bar (corner, clutching, etc). For just straight-ahead riding along? I wave at everyone. Just the lazy, left hand off the bar, dropping a bit lower and two or three fingers out. I'll say I get >75% returns.
*WARNING - the following is UNSAFE BEHAVIOR while riding a motorcycle*Recently, when I'm approaching someone who I suspect isn't going to wave (hard core sport bikers, hard core Harley riders) I'll go overboard and lift that arm WAY off the bar, wave my hand, and sometimes lift my left foot off the peg and partially stick my leg out at 'em as well. Sorry, but a guy did that to me one time and I had to pull over I was laughing so hard... Since then, I do it when it looks like they're going to be too serious.
I look back in my mirror, and I can just TELL they're looking in theirs to see who that guy was, and wondering if they knew me.
Whenever my son and I are riding together, he usually rides behind me, and I can see him shaking his head...
*end of UNSAFE RIDING*
So, keep on waving. Wave to 'em all!
Happy Riding!
Kirk