Maya Tip - Insert Keys Tool
Insert Keys. You don't always want to key all channels, sometimes you just want to insert some keys. There's a handy hotkey for doing just that right from within the GraphEditor.
The beauty of this hotkey is that it doesn't disturb your current curve tangents. We use it all the time to insert keys in the middle of a curve to just tweak it slightly, without having to mess with tangent handles.