Penang International Airport Guide
Penang's airport is Malaysia's second-busiest, after KLIA. The airport is rather small, making it a bit crowded. There's just a single terminal building on two levels. Arrivals are on the ground floor while departures are on the second.
As of early 2012, the airport was in the midst of a massive upgrade, that would probably continue for another two years or so. They are, in effect, building a new terminal building around and on top of the old one. They have completed work on a new domestic departure wing, so that now domestic and international departures are separated.
While the changes to the structure are massive, and there will undoubtedly be more shops and services in the airport when it's completed, the basic outline of using the airport probably won't be significantly different than what's described here.
In my experience, security at Penang International Airport seemed to be the most lax I can recall. There does seem to be a problem with petty crime at this airport, according to news reports, so watch your belongings.