My general suggestion is LEFT side for arrival. This gives you a nice view of Mauna Kea/Mauna Loa (if it's not voggy) and Haleakala as you close in on Oahu. Then you've got a nice view of the Ewa plains, Pearl Harbor (including the USS Arizona Memorial), and the Aiea area on final approach.
This all changes if it's Kona wind arrivals. If so, you need to sit on the RIGHT side. That approach will give you a view of Waikiki, Downtown Honolulu, and greater Honolulu on final. The only way to know if it's Kona wind arrivals is to check the weather reports. Anytime the winds are coming out of the South/Southeast, there's a possibility that there's Kona wind approach. But do note that this is fairly uncommon--probably about 75-90% of the time, it's the regular trade wind approach.
See
http://www.flyertalk.com/forum/hawai...ight=wind+kona
For departures, it's LEFT side of the plane during regular trade wind departures. RIGHT side of the plane will give you lots of views of water. LEFT side will give you views of Downtown Honolulu, Waikiki, and greater Honolulu. During Kona wind departures, you should still select the LEFT side of the plane, even though the aircraft takes off in the opposite direction since the plane will loop around and still give you views of Honolulu.