what i've learned

the first thing i learned (the hard way)

When you mount a lens onto a camera, you have to line up the red dot on the lens with the red dot on the camera body!

the second thing i learned (again the hard way)

You have to press the lens release button on the camera body to take the lens off.

the third thing i learned (still the hard way)

Each camera body, even from the same manufacturer, has the lens release button in a different place.