There really isn't a best age for kids to start guitar lessons, but most children under the age of 7 generally don't have the dexterity or patience needed to learn to play the guitar. With persistence and motivation some kids have learned to play guitar at some impressively young ages, but it really comes down to is the individual attitude and maturity level of the student. 
From a practical perspective, teaching yourself guitar may be the only option. Guitar lessons cost money. If you’ve just scrounged your pennies together in order to afford a decent starter guitar, you may not be eager to throw down another twenty bucks a week or more. Compound this with the fact that most guitar instructors have their own methods and will teach you at their pace, not yours. This makes sense from their standpoint, but it could get a little frustrating and expensive from your point of view.
Surprisingly, for a free site, Justin Guitar offers a few free tools and apps to help guitarists with their lessons. The most interesting of these are the series of apps available for download on the iTunes store (so they will only work with iOS). These include a Time Trainer Metronome, a Guitar Note Trainer, and a Blues Lick app – which brings together Justin’s weekly Blues Lick series.
I have been studying guitar off and on since age 10. I have had several instructors over the years but most of them didn't have a solid game plan, a horizon or timeline toward getting to the next level. Plus it was expensive. As technology evolved more Youtube videos came online. I tried teaching myself from the videos but the process and information was fragmented. Watching them felt like lessons from those in person instructors. I googled best online guitar courses and found Guitartricks rated at the top so I took a chance. I will tell you this, if you have the patience and dedication, and follow the course, especially Fundamentals I and II, you will be amazed at how quickly you will advance. As with any endeavor worth undertaking, it isn't easy. But, my instructor, Lisa McCormick, developed the Core system and she nailed it. Her gentle nudging even paced approach has helped me improve my playing and understanding of the guitar way beyond my expectations. The Guitartricks system is every bit a road map to get you from beginner to advanced, or if you choose, to be able to play some songs if that's your goal. A well thought out intuitive interface to navigate through your journey toward playing guitar. Two thumbs up Guitartricks!!!
Ryan was great! He's obviously a talented guitarist and he is very laid back and makes you feel comfortable. He shows you in detail what you need to do to become a better guitar player. My ONLY advice, and the reason he doesn't get 5 stars, is I think he should have more visual aids with his lessons. For example, write down the different scales or transcribe the first several measures of a song. Then, one has something to refer back to when you are practicing and invariably get stuck. Other than that, I would highly recommend Ryan as a guitar teacher!

The above diagram may look confusing... fear not, it's one of the most common methods of explaining notes on the guitar and is actually quite easy to read. The above represents the neck of the guitar when looked at head on. The first vertical line on the left of the diagram is the sixth string. The line to the right of that is the fifth string. And so on. The horizontal lines in the diagram represent the frets on the guitar... the space between the top horizontal line, and the one below it is the first fret. The space between that second horizontal line from the top and the one below it is the second fret. And so on. The "0" above the diagram represents the open string for the string it is positioned above. Finally, the black dots are indicators that these notes should be played.
I was lucky enough to meet Justin at the Guitar Institute during a summer school in 2004, and to have some private lessons with him afterwards.  He was the teacher who kickstarted my guitar career and persuaded me that I was ready to join a band.  That was 14 years ago and many dozens of gigs later.  I’m now just finishing a degree in Popular Music Performance.  Justin's online lessons are easy to follow and he has a manner about him which makes you believe that you can achieve.  Where he demonstrates songs, I have found his versions to be consistently more accurate and easy to follow than those of any other online teacher.  On this website you really will find all the skills and information you need to become an excellent musician.  Many thanks. Ian.
Play the song with the audio recording. Once you've mastered the individual portions of the song, you're ready to play the song in its entirety. Play the song and strum your guitar along with the song. Try to keep up with the tempo of the song you're covering. Follow the tabs as you play. If you mess up, follow the music on the tabs and come back into the song when you're ready. Once you've become proficient at playing the riff, continue practicing until you don't need the tabs anymore.
When playing the guitar sitting down, the body of the guitar will rest on one of your legs. In most styles of guitar playing, the guitar will rest on the leg farthest away from the headstock. This means, a person playing the guitar in a right-handed fashion will typically rest the guitar on his/her right leg, while someone playing the guitar in a lefty manner will rest it on their left leg. (NOTE: proper classical guitarist technique dictates the exact OPPOSITE of the above, but for this lesson, let's stick to our initial explanation)
'Artist Studies' here are a real highlight of this site. Twenty-nine 'In the Style of...' different artists are taught here, including The Edge, the great Albert King, AC/DC, BB King, Brian May, Eddie Van Halen and so many more. Pick your favourite and learn to play just like them. Includes all the information you could possibly need including set up your amp and guitar. The 'Practice' tab in the experienced lessons includes exercises to practice for the different genres. Again incredibly comprehensive and simple to get around.
My business was created because of one of the most powerful forces in the universe–love. My daughter desperately wanted to play guitar like her daddy. Like most new guitar students, she was having trouble learning to play. It pained her to quit but she was frustrated and was going to give up. My daughter came to me and said, “Daddy, can’t you do anything to help me play guitar?” I invented the ChordBuddy because I love my daughter and now, she plays and teaches guitar just like her daddy.
Of course, this top-down lecturing is all very abstract without examples. Let me give you the worst case scenario. My school talent show, 2008. Two friends of mine performED an ambitious but utterly inappropriate Metallica cover in front of the other students, their parents and the faculty. It was excruciating. Although the solos (presumably the only thing they had bothered to practice) were technically flawless, the whole song was undone by their terrible rhythm. The timing of the song became displaced, the chords were so badly fingered that it was difficult to hear the riff and consequently the whole performance fell apart. They looked like morons. They had sacrificed learning basic rhythm and paid the price. Make sure you don’t do the same.
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.