I just got back from Oahu.
I fished pretty much every day. I fished from the shore as well.
I've gone out on boats there, but I like shore fishing because you do things at your pace. I liked fishing on the beach in front of the house with a book in one hand and a beer in the other. (The rod was between my legs)
But seriously, I fished mostly North Shore around Haleiwa and Mokuleia. Man I was nailing fish everyday! Get the circle hooks size 16 is great. They seemed too small to me, but they were getting big fish. The great thing about Hawaii is that some of the biggest fish are caught right from the shore.
I like fishing off rocks that drop off straight down instead of surf fishing. I packed a small rod in the suitcase, so I couldn't really surf fish even if I wanted. But no matter what anybody says, you can catch a big fish on a small rod! Just don't run out of line. I hooked 3 fish 20+lbs. And this is just casual fishing. I used squid, and fish from the tidepools. Just buy a $3 net from the store and net the little gobies. They call them Jumping Jacks there.
The nightmare of the trip that I don't really like to mention was when I hooked a Sea Turtle. Seriously. I was a little North of Shark's Cove fishing off some rocks just straight down about 40 feet, and I just about lost my pole because he almost pulled me in. I didn't know what it was. I thought it was a 9' shark that didn't know it was hooked. I fought it for about 35 minutes, but then I saw it come up for air and saw that it was a Green Sea Turtle. So I immediately cut the line. I was so upset. I felt very bad. It is a resident Sea Turtle that I see every year when I dive at Shark's Cove. I know it's him because I've never seen a turtle so big ever. He has an odd lookin his eyes when he looks at you. It's like he's seeing inside you.
Anyways, I'm rambling. But good luck. I loved it. Not knowing a lot of the secrets, I just threw out the line and kept my fingers crossed. But it worked. I caught fish everytime, and never caught the same type twice. Use strong line, 20lbs +.
Good luck. Let us know how it goes or if you have more questions.