Go to the lovely little island Caqalai, where you can snorkel off the beach...and frankly there's not much else to do there apart from beach life and walking to snake island and at night you can watch the stars.
Ovalau watersports has useful informtion on their website on how to get to Levuka, accommodation etc.
This is also the place to go for booking activities
Walk around the streets squeezed in between Beach street and the mountains. You don't need to know exactly what to look for. Everything of interest is marked with a Levuka Hetitage Site sign telling you what it is.
Plenty dishes to choose from. Nothing extraordinary about the food, just a good option for a meal with a nice view in Levuka.
Favorite Dish: I had rice with vegetables and cashew nuts and a fruit drink. and came back for it a second time.
Levuka is so small you'll walk around it by foot easily. If you ever need to take a taxi (which I did because I had things to carry and was late) it wont get expensive, as it's too small to drive far.
In Levuka people actually say hello or chat with you out of friendliness, not to coerce you into buying something. I was shocked to arrive to Nadi and discover that the same kind of small talk there was not with good intentions. If you have been in Nadi before you come here, don't worry when someone start chatting with you. If they ask you where you are from, it's because they are curious on where you are from. No one is gonna try and sell you something.