Get a fast car or motorcycle and get on a highway or long road. Drive on the side of the highway you're supposed to be on, dodge traffic or stay in the middle of the lane and just speed and Stunt Points should come in really fast.
Go to the Panau Int. Airport and get the sports car at the entrance and drive it to a runway. Once a plane appears, go into the stunt position and use the grappling hook to attach the car to the plane. Once this is done, enter the car. The plane takes off with car in tow. The points begin to rack up quickly. As long as you don't release the grapple from the plane your car will just fly along with the plane.
When flying a helicopter with weapons, destroy as many military objects (SAMs, radar, vehicles, infantry, etc) as you can. Eventually Rico will hum the song "The Ride Of The Valkyries", which was played during the famous air raid scene in Apocalypse Now.
Get a light weight car or a light weight truck, then go inside the airport and wait for a plane to be on the runway. When a plane comes, grapple it onto your car and wait until it takes off. You will then be in the plane cargo.
Go to coordinates X7392, Y16151 to find a hot air balloon. Note: You can also find an armor piece near the balloon. You can ride the balloon by shooting off the sandbags and steer it by waking in the basket. Note: Unlike other vehicles, the hot air balloon can be used to fly over the Lost island without getting destroyed.
In the northwest corner of the map is an island separated from the mainland by a fair stretch of water. If you fly over this island in any plane you'll automatically crash. On the island you can find numerous references to Lost, including plane wreckage of Oceanic Flight 815, familiar settings like the stream. You'll hear sounds of the Smoke Monster as you explore too. The hatch is also on the island.
One type of boat in the game is named "Winstons Amen 69", which is a reference to a famous drum beat known as the "Amen Break" performed by the funk and soul band "The Winstons" on their 1969 album "Color Him Father".