Practice fretting the strings. The frets are the metal strips that run perpendicular to the strings that mark each note. To play a note, press your finger down between the metal strips, not on them. To say that you're playing the third fret means that you place your finger on the string in the gap between the second and third fret. If you hear buzzing, move your finger away from the lowest fret and closer to the higher fret. Hold the string down firmly so that it only vibrates between your finger and your strumming hand, with the tip of your finger doing the pressing.
Learn how to transition to different chords. One way to become proficient quickly is to learn how to transition between the various chords quickly. These transition periods are often the hardest for beginners to play when they are starting off. The more you practice between switching to different chords, however, the better you'll get at doing it in songs. Practice switching between open chords like G, A, E, and C. 
The guitar is a remarkably hackable instrument for a million reasons that will be revealed to you as you spend more time with it. As you go along in your journey you’ll find a million shortcuts and fun ways to learn fast. I’ve rarely heard any of this stuff from guitar teaches, so beware, trust your instincts, and learn from people who can show you where you want to be.
A child as young as 4 can begin to learn if they are really motivated and have a patient, creative, and devoted teacher. However, we've found almost all kids under six are too young to benefit from formal guitar lessons, as they require dexterity and levels of concentration children their age can't provide. That being said, lessons do not need to be formal right off the bat, and can just provide a fun introduction. Also, your child may benefit from using a ukulele to start, as it's smaller and easier to learn, but very similar instrument.
Justin, first off I just wanted to say thanks for all the advice and instruction. You make playing guitar easy and understandable and fun. You explain very well the hows and whys when presenting a new song to learn and walk it through so that anyone can learn. I have played guitar for 20 years now and have learned more from you in the last five years than the previous 15 by myself. You have also been a tremendous help to both my son and my daughter in learning to play as well by making playing fun and interesting. I have a couple of pictures of me and my children all doing what we love. Many Thanks to you Justin
Learn barre chords. Barre chords, or movable chords, are extremely useful for starting to play songs. In a barre chord (sometimes shortened to "bar chord"), the index finger of your fretting hand "bars" all the notes at a single fret. To play an F, which is the barre chord in first position, you bar all the notes on the first fret with your index finger and play what is essentially the shape of the E chord moved one step up the neck, with your middle, ring, and pinkie.
Determine the guitar riff that you want to learn. Listen to acoustic guitar songs that you enjoy and choose one that you'd like to learn. When finding your first song, try to find a song that has an easy chord progression. Listen to the song and determine how many chord changes it has and the speed in which the song is played. If there aren't that many chords or the song seems simple to play, you should choose that song as your first song to learn.
I have checked out Justin's site and found it to be comprehensive and informative. I have always felt that learning about music and especially music theory applied to the guitar, is helpful in finding your own unique voice on the instrument and expanding your creative horizons. Along with his insight into teaching and his fantastic abilities on the instrument, Justin has created a powerful go-to-place for anyone interested in exploring the instrument to their potential. Just don't hurt yourself.
Brent Bassham began playing guitar at the age of fifteen as a self-taught until he began his studies as a freshman at Tyler Junior College. His talents were recognized by his instructor Frank Kimlicko who awarded him with scholarships and twice as the Outstanding Guitar Student of the year. He has been taught by master teachers such as Brian Head (president of Guitar Foundation of America), Miguel Antonio, Grammy Winner Maestro Pepe Romero, and Grammy winner William Kanengiser. He has also been selected to perform in public master classes with: Pepe Romero, Angel Romero, Enric Madrigera, and David Russell. He learned a wide range of ... View Profile
Intermediate Guitar Class - Open to all ages, from age three to one-hundred sixty-three, but an audition or permission from the instructor is required. This class is intended to be challenging. Topics covered may include movable bar chords, song forms, repertoire development, fretboard mapping, improvisation, and other advanced techniques. New classes start every month and may be repeated as often as you like. Cost is $85 per month (4 hours).