what are bad habits you can get when you teach your self guitar?

Answer 1

it is tempting to avoid using your little finger in making chords.
also beginners have a tendency to tip the face the guitar upward so that they can see their hands. this makes many chords more difficult to play.

Answer 2

An other problem is the proper position to hold the guitar.
If you hold it right you can play for hours, hold it wrong and you get cramps, dead fingers and back aches in a short time.

If you get any pain or problem while playing, ask an other guitar player for tips and/or look at pictures or videos of professional players.