Because "Minecraft" uses a voxel engine, it is especially simple to navigate using coordinates in an (X, Y, Z) format. Everything in the world is built out of cubes laid out in a three-dimensional grid. It is handy to know how to use this to your advantage as you play the game.
Basic Coordinate Finding
You can access your current position on the grid from all versions of "Minecraft" besides the Pocket Edition. On computers, you can find it in the debug overlay accessible by pressing F3 on a PC and Fn-F3 on a Mac. On an Xbox console, you can equip an in-game map to view your coordinates.
Reading Horizontal Location Values
Given your position on the X-axis and Z-axis, you can find anything on the surface. The X coordinate gives your distance east or west relative to the origin point. The Z coordinate does the same for north and south. When tracking using the coordinate system, it is important to note that all positive values for X point east while all positive values for Z point south. It is a bit counter-intuitive, especially since it does not follow standard usage where Z is the vertical axis.
The Y-axis coordinate will always have a positive value. This is because the origin point on the vertical axis is the bedrock at the bottom of the world. The first five levels of every world are, in fact, an uneven layer of unbreakable blocks. Usually you will spawn between 60 and 70 blocks above that, near sea level. Your current Y position will never be above 255 due to the height of the sky box.
Making a Map
While it is possible to create in-game maps and chart your favorite areas, generally these don't prove particularly useful. They cover only small chunks of the surface and can be hard to read. As an alternative it can be helpful to keep a list of useful landmarks using their coordinates. Everything from useful materials you might need later to hidden dungeons you don't have time to attempt at the moment can be cataloged this way. That can be especially helpful on multiplayer servers where hiding your valuables in unobtrusive areas is an important tactic.