Servo motors have minimum and maximum lengths of PWM signal width in microseconds, that they would tollerate. But manufacturers never bother to display those.
What is the best way to find those out?
If you're talking about R/C servos, PPM pulses (not PWM) are usually in the range 1000 to 2000 usec, sometimes ±200usec, repeated roughly every 20msec
What are PPM pulses? Can Arduino do them?
I am just using the standard Servo library. I guess it is sending PWM pulses.
Why guess?
Nope - They're not PWM..
They are PPM - it takes 2 pulses and the time between the pulses controls the servo position.
What is the best way to find those out?
You use simple servo conrol code to send the servo increasing and decreasing control values and find the servo high and low hard stops.
They are PPM - it takes 2 pulses and the time between the pulses controls the servo position.
They are PPM, but the servo displacement is proportional to only the width of the control pulse; the time between pulses is largely immaterial (though it isn't recommended you change it!)