I lived there for three years in the late 1980s. At that time it was pretty easy to walk on to a charter out of Honolulu. But my favorite was flats fishing on the windward side of Oahu. You can wade out and fly or spincast. There's bonefish there but lots of other fish too. I knew some by Hawaiian names that I can't remember now other than one fish called a pappy, but plenty of beautiful and colorful fish. Don't be afraid to throw spinners right off the shore over the reefs either.
Edit: Just noticed you said you were going to Maui. I never shore fished there, but I would imagine it's even better than Oahu.
Edit: Just noticed you said you were going to Maui. I never shore fished there, but I would imagine it's even better than Oahu.