For some reason Maya by default tangents in the graph editor are locked up tighter than a beer cap without a bottle opener unless you do these steps.
1. Open the graph editor
2. Select all your keys in the graph editor (or juts the ones you want to effect)
3. Go to curves menu in the graph editor and choose "weighted tangents"
4. Then with all of them still selected goto tangents menu and choose "free tangents"
Now they should unlock and give you ALOT mroe flexibility in your graph editor.