I fly, at least 3-4 times a year. I always scope out any Arab or Muslim looking people, and look them in the eye if they'll make eye contact, just so they know that someone is looking. I watch them in the gate area before boarding, see how they move, who they talk to, what they spend their wait-time doing.
Then once on board the plane, I take note of people boarding as best I can, where they sit, and who is sitting with them. After the plane reaches cruising altitude, I get up and walk the length of the aisle, ostensibly to use the restroom in the rear of the plane, but sometimes if I'm seated in the rear I'll have to walk all the way forward and then work my way back, which draws looks from other passengers now and then, but oh well. On my way back, I do my scoping once again. I do this hoping to make direct eye contact with the same Muslims I made eye contact with in the gate, if there are any.
I have no idea if this is a practice useful enough to merit the effort, but it makes me feel better to have some situational awareness, even if I'm not fully equipped to deal with an event.