I think a sign of amateur writers is how often their characters laugh or smile. Not that misery is a preferred feeling, but if your characters are having a good time, we don't need to be told every time they chuckle.
I came across an excellent example of why this sucks. The infamous movie called The Room, written by, directed by, and starring Tommy Wiseau. Aside from the fact that this movie is 30 kinds of garbage rolled into one, I found a clip of how obnoxious random laughter is.
Watch this video of every time characters have a laugh. When I watched it, I swore I could see the script saying "Tommy laughed." It also showcases the awkward greetings littering the screen.
Quite simply, if characters keep doing the same thing over and over, cut it out. Count the number of times they laugh or shake their head or turn 180 degrees or do any other minor tic, especially during conversations. If it ends up sounding like that video, then revise and revise and revise some more.