Don't approach or talk to anyone - just lean against the wall, alone,cigarette in hand, gazing at the floor lost in thoughts or staring, forlornly, at the ceiling. Be strong and silent but with a hint of vulnerability.
Or
Sit at the end of a bar, alone, cigarette, lost in thoughts, indifferent to your surroundings, slight look of indignation on your face. Be strong and silent.
Or
Stand in the middle of a room, alone, cigarette in mouth, hands in pockets, eyes scanning your surroundings with an ambiguous look about you. Be dark and mysterious.