What's the easiest way to draw a 3d cartesian plane?

I see 3d graphs represented in a number of different ways.

Some are like the first images, others like the second, others a different way entirely: http://imgur.com/a/cozSu

I recognize that these are the same thing, simply from a different perspective, but I'm wondering if there's a way that's easiest to visualize with or most commonly used.

Regards