I believe the most important thing to develop in a beginning guitarist is a solid technique. Teaching technique is basically teaching someone how to play the instrument. While this seems like the obvious first thing to teach a student, it is astounding how many teachers completely ignore technical training. Instead they take a teach by doing approach, teaching songs from the beginning without teaching the underlying skills needed to perform these songs properly. Occassionally one gets a naturally gifted student who is not harmed by this method (or lack of method) but the majority of students end up developing bad habits. These bad habits will inevitably create problems once the student starts playing more difficult music. The frustration encountered by students who develop poor technique can often lead to them quitting the instrument as it is a constant struggle to make the music they are playing sound good. Students may think the fault lies within themselves due to a lack of talent or ability when it is more often than not the lack of proper instruction that has caused their deficiencies.
When guitarists develop poor technique they usually have to undergo remedial training, to a certain extent learning to play the guitar over again, if they want to improve their playing. While necessary, it is much less enjoyable to do basic technical excercises after you have played the instrument for a while than when you are first learning. In other words, it is much better to learn to play guitar correctly the first time than to learn it improperly and have to relearn it.
My approach is to teach the underlying techniques first and then carefully choose the songs that are played so that they are songs using these techniques and not other techniques which have not yet been learned. Obviously if a student only has technical exercises to practice they will get bored so I try to maintain a balance between technique and playing songs that use the learned techniques. For example, I teach the pentatonic scale quite early in the course of study as this is both a useful scale for developing hand position and one which can be used to make enjoyable music. With this scale students can create improvised lead guitar solos over blues or rock songs played by another guitarist, on a CD or from a website. Thus, they are making music and having fun while at the same time developing their left hand.
Different styles of music require different levels of technique but the underlying guitar technique itself is the same. Many rock and pop songs are not very difficult to play and do not require a very developed technique to perform them. This is why many poor players can still manage to play such music. In fact, often the performers in the bands themselves have poor technique and are not particularly good players. Such players will, however, have great difficulty if they try to play more technically difficult music such as a piece by Bach, a jazz standard or a rock song that is more complicated and requires a certain degree of technical proficiency. It is my goal to develop my students' techniques so that they can play whatever style of music they want at any level of difficulty. Many students start out wanting to learn easy power chord pop songs but become more ambitious in the music they want to play once they are able to do this. Solid technical training gives students a foundation on which they can build and allows them to sucessfully learn increasingly difficult music.