Here's some advice that Pat Hanrahan gave me in 1994 
for structuring a job talk.  It's reproduced below,
with my own additions and interpretations.

Title
    [ something accessible to a broad audience ]

Introduction 
    [ what is the context?  what is the problem? ]

Motivation 
    [ why is the problem worth solving? ]

Challenge 
    [ why is the problem hard? ]
    [ if it's important, why haven't others solved it? ]
    address theory 
    address practice

Major idea 
    [ what is my contribution ]

Technical aside 
    [ why am i good at this ]

Implementation and results 
    [ demonstrate ability to produce scientific results ]

Summary/contribution 
    [ what should the audience take away ]

Future work & vision
    [ demonstrate a coherent, interesting plan ]