The mango has a flat, oval-shaped pit in its middle, and you want to slice downward on either side of the pit to free the flesh. Hold the mango with one hand and stand it on its stem end. Slice from the top of the mango, down one side of the pit, then repeat with the other side. You will end up with 3 pieces: 2 halves and a middle section with the pit in it.
Take a mango half and cut a "crosshatch" pattern in it, making cuts lengthwise and crosswise through the flesh, but stopping at the peel.
If you're eating the mango on its own, go for it! Peel the cubes off with your fingers — or, better yet, bite them right off the peel. If you're using the mango in a recipe, then cut the cubes away from the peel with the knife.
Peel the strips of skin off the middle section and nibble as much fruit as you can from the pit.