Once you have made it to your first lesson, there are some questions you should consider asking. Ask the guitar teacher about their experience. How long have they been playing? How long have they been teaching? What are they best at? What styles do they teach? What is their method of teaching guitar lessons? What extra resources can you use to further your learning? It is key to ask these questions and listen.
I have heard how giving you are in so many respects of music schooling and I must say that I am impressed. You remind me of the pure idealism that we had in starting Apple. If I were young, with time, I'd likely offer to join and help you in your endeavours. Keep making people happy, not just in their own learning, but in the example you set for them.
I've seen so many guitar lessons where the instructor simply dives right in and begins teaching chords. Unfortunately, that assumes that the student's guitar is already in tune! Guitars are made out of wood, and wood reacts to our environment, be it hot, cold, dry or humid. As such, guitars frequently go out of tune, and they must be tuned to make them sound good. If you begin learning to play guitar on an out of tune guitar, it will not sound good to the ear no matter how hard you try, and as such, it will become discouraging pretty quickly.
Justin Sandercoe has thought long and hard about how to teach people to play the guitar, and how to do this over the internet. He has come up with a well-designed series of courses that will take you from nowhere to proficiency. I tried to learn how to play years ago, using books, and got nowhere. I've been using Justin's site for just over a year and I feel I've made real progress. What's more, Justin offers his lessons for free - a boon for any young player who has the urge to play, but whose pockets are empty. I've seen and used other sites for learners: none of them offer as clearly marked a road as Justin does.
C-chord: Place your ring finger on the third fret of the fifth string. Place your middle finger on the second fret of the fourth string, and your index finger on the first fret of the second string. Strum all but the sixth string. Then, go back and play each string individually, while still playing the chord. Make sure each string rings out clearly.
Learn how to read tabs. Tabs will have six lines that represent your strings, along with numbers that designate where you should be placing your fingers. The numbers represent the fret in which you need to hold the string down. A 1 means the first fret, a 2 means the second fret, and so on. Numbers in a progression mean that you hold down the first individual fret and pick the note, then move to the next one, and so on in succession. Numbers on the same vertical line are meant to be played together simultaneously as a chord.
When you play the right note or chord, you will hear it. It will be a pleasant sound, it will be clear and won't have any blocked string sounds (unless it needs to, but you'll get to that later). To play a note or chord correctly, you have to get your fingers in the right position and press as hard as you can on the frets; it will become a habit if you practice enough.
Practice at least 20 minutes 6 days a week. Consistent practice will allow you to improve your guitar playing skills over a short period. Taking long breaks and not staying dedicated will wear away your muscle memory and delay the development of your skills. Instead, dedicate 20 minutes to an hour of practice throughout most of the week. During practice, you can either run different drills or you can try covering a song.
Learn the difference between chords and single notes. Chords occur when you play two or more notes on different strings simultaneously to create one unified sound. These are what make up the "rhythm" portion of acoustic music. Single notes are used more for solos and occur when you play a single note at a time. Both are skills that you must become proficient in when learning to play the acoustic guitar.
Beginning Guitar Class - Open to all beginners age 13 and up, or intermediate players who want the review. Begins with holding and tuning your guitar, names of guitar parts, and quickly progresses to chords, scales, tabulature, and playing basic songs. A variety of styles are introduced to encourage students to explore and find the styles they like best. Classes are organized according to age and skill level, so it's an easy way to make new friends too. Classes start every month and may be repeated as often as you like. Cost is $70 per month (4 hours).