OK, so I started reading a lot about guitar theory recently and how to pick up songs by ear. My friend suggest me to get a slow, simple song based on the C scale, and try figure it out slowly.

The problem is, I don't know any such songs (to be honest, I don't know how to identify a song's key unless I look at the tabs, and that kills the whole purpose of the exercise).

If anyone could give me a slow song based on the C scale and possibly the position (C, A, G, E, or D), that would be vastly appreciated.

Also, if anyone can add any tips it would also be appreciated.

Thanks in advance.
You should take note that there isn't just a C scale, it's C major or C minor. These are the predominant keys of all music.

If you're looking for a song suggestion, use the suggest me a song thread.
And no, Guitar Hero will not help. Even on expert. Really.