The state of Texas via the Texas Real Estate Commission has created a standards of procedures that all home inspectors in Texas are required to follow.  The entire SoP can be found here:  Standards.

Briefly, we are looking in five basic areas plus optional items:

I.  Structural Systems
    * Foundations
    * Grading
    * Roof Cover and Structure
    * Doors and Windows
    * Fireplace
    * and more!

II.  Electrical Systems
    * Electric Panel
    * Branch Circuits

III.  Heating, Ventilation and Air Cond.
    * Heating
    * Cooling
    * Ducts and Vents

IV.  Plumbing Systems
    * Water Fixtures
    * Drains
    * Water Heating Equipment
    * Hydro-Therapy Equipment

V.  Appliances

VI.  Optional Items
    * Pools
    * Sheds
    * Sprinklers
    * Septic systems
    * and more