Collocations for smug - adj.

appear, be, feel, look, seem, sound
get
Now don't get smug just because you've won a couple of games.

extremely, fairly, very, etc.
incredibly
the incredibly smug expression on his face

almost
a little, slightly, etc.
annoyingly, insufferably, unbearably
He is insufferably smug and arrogant.

about
What are you looking so smug about?

Smug is used with these nouns:
expression, grin, look, satisfaction, smirk