I second the Get a teacher advice! you'll accomplish more in the first year with a good teacher than ten years without!
Learn to read music is another really important one. Aside from tabs being very limiting to work from there are also limited tabs available. Notation opens up an entire universe of available music, including everything ever written for other instruments (when you get to a level of being able to transcribe from one instrument to another and desire to do that).
Also like the Frederick Noad solo guitar playing books (level 1 and 2) whcih are full of nice little pieces to work on and great study notes for each. But get a teacher as well, and use the Noad for reference and/or work on it with you TEACHER.
POSTURE!!!!!!!! make sure you start off by learning the correct (or A correct, as there is not just one correct way) way to hold the guitar. Very important to avoid injury! If you only take one class with a teacher FIND a teacher to help you cross this bridge. DON'T try it alone. You can look at youtube videos until you're blue in the face but only a teacher can take into account your particular size/shape and body style and this is perhaps the most important element to playing guitar as incorrect posture will not only be uncomfortable and cause pain, it can cause permanent injury.
If you don't have a semi decent student guitar I highly recommend getting one. It's really frustrating trying to learn to play an instrument that not even a seasoned pro could make sound good. Doesn't have to be super awesome but a 100$ walmart special definitely won't cut it. Best entry levels I've seen are the Yamaha sg151's. I did a lot of reasearch before picking one up as my go-to/ take it camping guitar. They can be gotten pretty cheap. Next, have your guitar setup to play easily... Very hard to learn on a high action guitar... Make sure that it at least meets the 4MM(bass)3mm(treble) at 12th fret guideline as a maximum. I've played for years and have trouble playing action mmuch higher than this. A good guitar tech can get it set up even lower than this without too much expense. If you buy a new one make sure it is set up well or that they will include setup in the proce of the guitar so you don't have the added expense.
Personally I also recommend (if you're totally new to the guitar) continuing to learn a bit of chord based styles of music as well. I.E. Classic rock or pop. A lot of folks will disagree with this one but I find it helps a beginner get a little more enjoyment out of it much sooner and gets you familiar with the guitar neck, chordal structure etc. Basically one can be playing simple 3 chord songs within a few weeks and playing them well within a couple of months whereas classical can take several months before you are playing music that you are happy with. It also helps to strengthen the hands. Think of it this way... A person that wants to become a great soccer/football player can still benefit from riding around the river trail on a bicycle or jogging in the park with their dog. However, do use good posture even when playing chord based styles and avoid strange hand angles and guitar over right leg while slouching in a chair. Not necessarily full on classical posture but find one that gets the guitar into a similar position.
And don't forget to have fun. If you don't enjoy it, you really have to have lot of discipline to continue. Also if you don't enjoy it, neither with your audience...
One Ring to rule them all, One Ring to find them, One Ring to bring them all, and in the darkness bind them.