1)BASIC UVMAPPING
2)THE GIZMO GRAPH
 
 

1)BASIC UVMAPPING

Let's start with an easy one.UV mapping Primitives like spheres,boxes,cylinders,planes etc.
Before starting uvmapping make sure you have the texture loaded and the material assigned to the object(mesh).
Now go to the Modifiers tab dialog.Select UVmapping and press the Modify button.

A dialog will appear from which you can choose the type of mapping that better suits the primitive object.
If it's a sphere then do a spherical uv mapping.Of course this still depends on what you have in mind but for now let's do the basics.Your choices are: Box,Cylindrical,Spherical,Planar.X Y Z radio buttons are used for defining the facing or orientation axis.To understand this better see the images below.
 
 
 
 
 
 
 
 
 
 
 
 
 
 

I use planar mapping so that the gizmo(yellow rect) shows the orientation:

The Fit button  is used in cases where the XYZ sizes of the object are not the same and you need to wrap the object.
Normally the > axis size is used for all gizmo's XYZ axes sizes.
A)No fit for BOX with X axis size > YZ:

B)Fit for BOX with X axis size > YZ:

U,V values are used for scaling.i.e.: if you wanted the texture tiled 2 times you should set value 2.
Flip check boxes are self-explanatory.

Continuing with the sphere:
Press the Apply button and the object is uvmapped.If not satisfied Undo and try again.When finished press the Modify button to get out of the UVmapping modifier mode.NOTE: If the texture is upside-down check the Flip V button to flip vertical.