The simplest act you can perform as a CA Operator is to smile and wave.
If you can't form a genuine smile, just wave, but don't sit there like a typical high and tight hard-ass staring at people.
Don't force a smile, either. You'll look stupid. Stupid people become targets quickly.
And don't wave big like a kid at the circus. Simply raising you hand deliberately and moving it a bit will let those you are greeting know that you mean no harm.
When in doubt, say nothing.