i did think about going by bus, but from what i could see they were pretty infrequent and i didn't want to spend all day waiting for the bus, so we took a private tour with GoShuttles (luke) and it was so relaxed and he's a great guy.
we also drove to the North Shore beaches to have a look (turtle beach) and to a lovely little town called Haliewa - this was such a cute place with really lovely atmosphere and some great places to eat.
another place Luke took us was to Waimea Valley and had a quick look around- what an absolutely gorgeous place - with a waterfall (if you have the time) which is reached by some sort of shuttle bus.
there are peacocks running around and gorgeous tranquil gardens.
Because we had limited time, our tour was only four hours but i would definitely go back and spend more time in both Haliewa and Waimea Valley