From BlenderWiki

Editing Ipo Curves and Keyframes

You are not limited to the Ipo Editor for Ipo editing, you can also add/modify/remove keyframes:

• in the timeline
• in the 3D view
• in the Buttons window
• ...and last but not least, you can record an object’s movements from the Game Engine!

As there are many different ways to work on Ipos, this is quite a big topic. For this reason we won’t detail methods that are very similar to those used to select/edit standard objects (especially for curves).

To avoid very long pages, we split the topic in two:

Editing curves

focuses on editing whole Ipo curves, as well as their properties, like interpolation and extrapolation types…

Editing keyframes

focuses on editing the “shape” of Ipo curves, adding keyframes, etc.