Regardless of the type of music you listen to or want to play, here is a short list of things you MUST know and practice.
You can use word association to easily remember string names E-A-D-G-B-E: Elephants - Always - Do - Good - Before - Eating (E-A-D-G-B-E). That might sound silly, but children love it and adults think it's funny that they can't stop laughing. Try it yourself and say it out loud!
This is an absolute must!!! Once your guitar is in tune, you will be able to develop your ear. You will hear things how they should or shouldn't sound. This is the first thing you should do when you pick up your guitar.
The human hand is an amazing thing and your fingers are delicate. When a beginner plays their first chord it is usually the same for everyone: You apply the death grip and your finger tips hurt. Well, honestly there is no way to get around it except practice, practice, practice.
Learning and practicing two chords is really boring. However, keep in mind, you need to get your fingers do something they have never done before. Challenge yourself: Can you play the chords correctly? If your hand was on your lap and somebody said, Play G!, could you play it? The important thing to remember here is just because you can play a chord or a scale, does not mean you can apply it. Master what you've learned, then move on. If you are not in the mood or without ambition, do not force it. If you force something, you will not enjoy it.
There is plenty of material on the Internet or your local book store to help you out. Use it all! Hang out with guitarist above your level.
Listen to your body. If it hurts, stop playing. Lastly, sit up straight!