I know people have been saying a lot of the same things but: Ever since I was trained by someone who actually knew what they were doing, and had actually worked on shows that weren't in a little old barn in the middle of vermont, I was taught to always wait for the cue and never do anything without the SM.
There have been times when I have been working on high school dance concerts or in
community theatre when I have questioned the SM because they weren't on top of it. There were a few times when I have taken cues on my own, I think they've all been smaller thing, that the SM would not call on a regular basis, and if I didn't do it the lights looked like crap.