Since I listen to a whole slew of things, I had to find a compromise that would suit everything. I ended up with an almost stock and neutral setting.
Bass: +1
Mid: +2
Treble: +1
Fade/Bal: -1/0
(each "point" is basically 1 notch on the slider on the touchscreen. That's actually 2 buttons presses to make it move a full notch).
I find that this is kind of that sweet spot between listening to music via USB or line-in, podcasts via Bluetooth, or sports or news radio (aka fuzzy, muted AM band stuff).
AM sports radio to listen to games is really soft and slightly muddy, so I have to boost the Mid in order to hear the voices better. This also helps with podcasts which are just pure vocals. Boosting the bass a little bit helps even out the increased mids; it prevents the mids from being too in-your-face. Increasing the treble helps boost up low quality podcasts as well as sports radio, while also improving a bit of the higher range stuff in music that's not produced in the front speakers.
Pushing the Fade back -1 is just my preference. I don't like loud music blaring in my ears. Pushing it back makes it feel a bit more balanced to me (i.e. front sounds equally as loud as the rear).