Candid shot critique

I understand that there are things in a candid shot that are out of the photographer's control. What kinds of things ARE in the photog's control other than basic camera settings?

in this shot, I had been trying to get panning shots of the trucks in the mud bog when I noticed these two walking through the crowd, so my settings were lower than I would have liked.

Canon EOS Rebel T2i
75-300 non-IS lens at 205mm
F/5
1/320sec
ISO-100
Center focus on the guy.

This is the jpg right out of the camera, with no post-processing.

IMAGE LINK: https://flic.kr/p/nL9S​6j

Framing and composition are under your control......if you view a potential shot that has neither, you don't have a shot. Timing of a shot is also key......be patient and anticipate.

...or if you can't be patient, rattle off a few shots - a scene like this is changing all the time.

The muddy couple appear to be the subjects. However, there's a lot of busy stuff going on around them. A tighter crop might help. Waiting for the guy in the orange shirt to get out from behind the woman would have helped, as well as maneuvering to get the white pole out of the frame. Lastly, the shot is a touch overexposed.