How Does One Paint Isometry?

The usual drawing order is
1
2 3
4 5 6
7 8
9

But then tile 5 will overlap sprite moving between cells 2 and 3

And you can't draw underlying tiles before the sprites, otherwise large sprites would mess the higher level tiles. Typical tile cubes in games like X-Com and Magic & Mayhem are 32x32x16 (allows modelling nice curved terrain), while sprites are several times higher to maintain proportions

>>1
Just draw whatever is further away first. If the sprite is tall enough to block a higher level tile, draw the high tiles first. Otherwise, if the sprite is short and below the higher tiles, then draw the sprite first.