How would you survive if you were stranded on an island?

You pretty much have to search the island for all means of food and shelter.

You could survive on an island by drinking coconut milk. Eating the citrus fruits from the trees. Also with the coconut, you can get the coconut oil on and rug it on your skin to prevent sun burn.
Fish if you can and hunt to get meat. Make a rod with materials around you. You can spear for fishes too.

You should try to look around the island and search for human made products that could be useful. Like a tin can. You then can boil water in it.
Find or make a place of shelter and start a fire.