What's the proper way to plug/unplug a laptop?

My plugs always sparked or zapped when plugging them in the wall, or extention cord to charge my laptop (Lenovo ThinkPad T410) I've used the manufacturer AC Adapter with cord, as well as a generic one. I've tried plugging and unplugging both ways. I've fried 2 cords so far. Is there a proper way to unplug/plug an AC Adapter with cord for a laptop? I don't want to keep buying new cords, etc.

Turn it off at the wall first… Gees… Why is life so hard… Lol

When you plug-in power supply make sure first laptop is turned off.
Before unplugging power supply turn laptop off