Playing the guitar could be simple, and you can get started fast with a few tips. Getting good at it, however needs a bit more of a structure and a system.

For now, let’s get you started with a few instructions that could help you get started fast as well as techniques that will impact how you will continue to improve in the future.

Two of these instructions are related to your posture and your guitar chords finger placement.

Your posture allows you to get your body and your fingers into the correct position so that your fingertips make the right contact with the string and provide a rich sound.

An arm-less chair or comfortable bench is a good start. If you don’t have access to it, sit at the edge of the chair or your bed so that you can move your arms without restrictions.
For classical guitar players, posture is part of the performance. They use classical posture that places the guitar on the same let as their fretting hand. If you are right handed, your fretting hand and the leg your are using to support your guitar would be your left leg.

When learned, I found it easier to place the guitar on the same leg as my strumming hand. That allowed me to reach under and around the guitar.

As far as finger placement, you need to place the thumb of your fretting hand behind the guitar neck, directly behind your fingers. Keep your thumb straight pointing up. There is a nice video that covers this basic technique at guitarresources.net that helps you see exact what I mean. Position of your thumb determines the reach of your fingers and stress on your wrist. You need to get this right.

Keep your elbow away from your body. If you keep your elbow too close to your body, it will make it hard for you to move your hand through the chord changes.
Your most effective finger placement for great sound happens when the tip of your fingers come in contact with the string. If your fingers are too flat, the sound quality drops and your could also touch other stings accidentally.

Proper posture and finger placement are two techniques that help you as a beginner guitar player and for a long time.