Dead Island Walkthrough Part 5: Act 1 - Resort - Ch. 2 - To Kill Time
Talk to Sinamoi in the Radio room in the lifeguard tower. He will tell you that you need to take care of food, and that you have to help Mike and Dominic.
Talk to Dominic just outside the room. He will tell you he needs an amplifier and to go get it from the lightouse.This will grant you the side quest: On the Air.
Next, talk to Mike who is standing downstairs in the porch, just outside the lifeguard station. He will tell you that the zombie corpses are causing bad smell and could attack other zombies, therefore they must be burned. He will ask you to go find and get gas from a gas station.
Once you help Mike and Dominic with their side quests, the main quest will advance.
Make sure to talk to everyone in the light house to get all available sidequests.
Before starting Ashes to Ashes, talk to Hank about fixing the Truck. Having the car fixed will help you transport gas to Mike faster.
For help with the sidequests, see our sidequest guide.