Just a few points that might help…
1. Beginners are mesmerized and dazzled by guitar frets, the mathematical and sonic relationships waiting to be discovered with a rubix cube kind of wonder, it’s evidence of the guitar players preoccupation with the left hand (fretting hand) and subsequent “box playing.”
2. There’s often ideas about using one method over another to improve quicker; these are analogous to a baby learning balance and walking (these things have to be done in their own time). In the early beginning there’s simply nothing that replaces hurting fingers and awkward right hand (strumming) clumsiness in coordination. It simply must be toughed out before the application of any ideology or music is applied. That being said, having someone personally teach you will raise you faster.
3. In contrast to piano leaning (and reading) guitar players typically learn pieces of songs instead of entire songs. The intro to Led Zeppelin’s “Heartbreaker” but not the guitar solo or the chords to a Tom Petty song but not the Jeff Lynne guitar solo. Why? See #9.
4. Rhythm is the hardest because it must be sustained and little can be sustained for long because the guitar is physically challenging. The shortest way to this seems to be to player easier material, despite most beginners being attracted to more advanced guitar displays -thus you have a lot of great guitar “licks” being played really badly at guitar center.
5. Few instruments contain a layout that faces “away” from the player: In order to see what is being played a player must turn the guitar “up” causing strange left hand problems, or tip their head “over” so they can see what it is that they’re playing causing neck pain. Advanced players don’t often look at the neck.
6. As the unschooled counterpart to the piano the guitar is historically the peasant instrument. Most guitar players don’t read, don’t cross pollinate well with other musical styles, and not until this last century, agree on a few things about the instrument (thanks largely to Andre Segovia). Playing music will always be more important than reading music, the guitar proves that but the guitarists that read have access to much, much more (imagine not being able to read language right?).
7. A little goes a long way. Playing every day for 30 minutes inevitably improves you rather than trying for marathon sessions. While this is true for most things, the physical difficulty of the guitar makes this even more true.
8. There are no “correct” ways to achieve sound on the guitar. Wes Montgomery used a thumb instead of his pick, Django Reindhart achieved velocity with two working fingers and Jimi Hendrix used his thumb. Also, there are no “correct” ways to left hand finger chords, if it works for you then do it. I get my students to “tamper” with all of the right hand methods.
9. Historically the guitar is an accompaniment instrument to the voice and not a solo adventure (Flamenco music, early European music, or Blues music). “Soloing” is a relatively new concept and thus the exploration of sound, electric guitars, effects, and amplifier combinations. Accompanying and soloing compliment each other and are of two different mindsets, thus beginners learning both in an entire song is seldom.
10. Beginners tend to want to do to much. It’s important to skip around and have different things to play and work on but the advanced idea is that the beginner really wants to focus on just a few things and really work them until they’re solid. It’s a greater use of time to get really good at a few things versus lightly touching on everything.