Cool little feature I found whilst poking around the graph editor: Buffer Curves. These are like alternate versions of your curve you can use to make changes, if you want to experiment without losing your original data.
To see them, you have to go to View > Show Buffer Curves. Like so:
You probably won't see anything for now, but if you start to move keyframes or adjust tangents, you'll see a dark grey curve in the shape of the original. The nice thing about this is it lets you strip out or add keys to your new one, without messing up the old, which is great for experimenting with different overall curve shapes.
To switch between them, just go to Curves > Swap Buffer Curve, and it will invert which is the active curve and which is the buffer.
EDIT: Forgot to mention, the buffer curve won't show unless you have the curve selected, to stop them cluttering up your Graph Editor.