Assume commercial operations for all these-

-Whenever engine is on, beacon is on. 

-Nav lights are, in general, on shortly after startup. 

-Taxi lights on for taxi, if desired (duh)

-When cleared for takeoff, or during runway lineup, turn on strobes and landing lights.  The important thing to remember here is that these don't go on unil you're on or very near the runway.

-Above 10,000' MSL Landing/taxi lights off, when descending back through 10,000' MSL turn 'em back on.

-once you've cleared the runway after landing, landing lights and strobes off. HOWEVER: Whenever you cross an active runway, it is recommended you turn on strobes again, and then turn them back off once you're off the runway (this can be done quickly by hitting O)

-nav off once you're at the gate (unless it's night ops, in which case leave them on-they often do in real life AND the instrument panel lights are tied to them in many default fs planes)

-beacon off when engines are off

There ye go!

Another thing, sorry for extra post.

In small GA operations in America anyways, all use of lights in generally considered optional during the day. You should use at least the strobes when flying for safety purposes, and the landing lights during takeoff and landing, despite the short bulb life.
At night, it's considered a good idea to fly with nav, beacon, and strobes on. Taxi and Landing lights can stay off except for takeoff and landing.