Settings

To add a cloud use the add menu:

Shift + A > Volume > Cloud

These are the settings that lets you control the overall look (modifier settings):

Seed (integer) - Creates a random cloud on every seed.
Detail (integer) - Iteration count on generation detail.
Puff # (integer) - Number of initial spawn points.
Distribution (vector) - 3D distribution of spawn points.
Features (float) - Amount of points to add (per area) on every iteration.
Mesh (boolean) - Shows underlying mesh.
Volume Density (float) - Multiplier for density field.