Playing music can be a creative experience, and an emotional experience, but it's also a physical one. And just like any other physical pursuit - batting, knitting, scrimshaw - you need to get the fundamentals down before you can really get down to the business of actually making music. There are a lot of little snags that you can encounter along the way. Let's look at some of the more common ones I've encountered in many years of teaching.
Fretting Hand Posture
One of the hardest chords for beginning guitarists to play is the regular first position F chord. There's something inherently uncomfortable about that combination of a first-fret barre and the need to firmly hold down the root note on the third fret of the D string. Perhaps it's because there are no other 'standard' open position chords which require barring across two frets. But you can learn a lot about your playing technique by how you fret such a notoriously tricky chord. Usually when I encounter a student who has trouble with the F, it's symptomatic of a larger problem with their playing posture. They often have the guitar neck parallel with the floor, and this puts the wrist at a very uncomfortable and unconventional angle. But there's a very simple way to fix this, and it'll make it easier to play pretty much everything else too. Here's the trick: First, without a guitar in your lap, bend your left elbow (assuming you're a right-hander) and observe the angle that your wrist is at when left to just naturally follow the contour of your forearm. Then, pick up the guitar and place the neck in your hand at that angle. You'll notice that it's much easier on the wrist. That's because you're no longer contorting your wrist to conform to the guitar: you're moving the guitar to fit with where your hand naturally belongs. This takes a lot of pressure off the wrist, makes it easier to move around the fretboard, and it even helps to give you more control over bends and vibrato. And it definitely makes it easier and less fatiguing to play for long periods.
I had a student once who had been learning from a different teacher for two years, but wasn't getting anywhere with his playing. When he came to me he wanted to try a fresh approach and see where it'd take him. As I always do when I start working with a new student who's already been playing for a while, I ask them to play something for me so I can get an idea of where they're at. I expected this dude to have a few tricks up his sleeves after two years. But - with all due respect - he was terrible. There was nothing wrong with what his fretting hand was doing, but his picking was all wrong: he was picking every note as an upstroke, and for two years his previous teacher hadn't pulled him up on it and tried to correct it. All of his chords sounded wrong and he had no sense of dynamics to speak of. It took a few weeks of picking drills to train him to play with downstrokes, and part of this involved exercises with up-down-up-down picking just to give him a comfortable place to start from, but before too long we were able to retrain his picking hand to play with downstrokes as well as upstrokes, and his playing started to display a sense of rhythm that he wasn't able to get across with upstrokes alone.
Some players have the innate ability to make you forget they're playing in an odd time signature, just because they do it so naturally. Alex Lifeson of Rush is a great example. But if you're not used to odd-time riffs, they can sound stilted and mathematical. The best way to tackle this is deceptively simple: just hum the riff. It doesn't matter if your pitch is off when you do this: what really matters is the rhythm. When you do this it seems to unlock the pulse of the riff, and you can then translate this back to playing guitar. And this doesn't just go for odd meters. It can also work for anything in 4/4 or 3/4 that you're having a hard time wrapping your fingers around. A personal example is the repeating solo figure beginning at 6:19 in Led Zeppelin's “Stairway To Heaven.” I had the tablature in an old Guitar World issue but I just couldn't seem to make the notes slot into where they should be. So I sang the lick instead, and sure it probably sounded rather silly, but once I'd made that connection with the rhythm it was pretty simple to transfer that rhythm back to the guitar.
Breaking The Pentatonic Rut
There's a whole book's worth of potential tips for breaking out of the Pentatonic Rut, but here's a great place to start: break the Minor Pentatonic scale out of its two-note-per-string configuration and turn it into a three-note-per-string scale. This forces you to move out of the box position and sets up some different note relationships. In the tab below you'll see two versions of the Minor Petatonic scale in the key of A. They both contain the exact same notes, but the second version will take you all the way up to the 17th fret, and will also give you room to expand even higher. I've included a few slides that will help you move around the scale a bit more easily. And once you start to explore the wider intervals that naturally present themselves in this scale configuration, you'll enter that Eric Johnson kind of territory where pentatonics take on a slightly more exotic yet still familiar feel.