I've listed down most of the basic concepts and techniques one should learn. But you get to decide what you want to learn. So choose, or bring something new from the internet that fascinates you. I'll do my best to help you learn it.

Concepts and Techniques:

1. Anatomy of the Guitar
2. Holding the guitar and plectrum (pick)
3. What is sound and how is it generated in general
4. How does the Guitar generate sound
5. Understanding Standard Tuning, and Tuning the Guitar
6. Changing the strings of the Guitar
7. Playing open Notes (Right Hand Exercises)
8. Finger positioning
9. Playing closed/individual Notes (Left Hand Exercises)
10. Understanding Tone and Semi-tone jumps
11. Finding Notes on the entire Fret-board
12. Understanding Natural and Accidental Notes (Sharps and Flats)
13. Playing Chords (14 basic chords)
14. Reading and writing Chords
15. Reading and writing Tablatures
16. Learning Strumming Patterns, and Muting the Guitar
17. Switch Guitar Chords with ease
18. Concept of Power Chords and Barre Chords
19. Major and Minor Scales
20. Making chords with the help of scales
21. Finger Picking
22. Learning Hammer-ons and Pull-offs
23. Learn Sliding and Bending techniques
24. Reading and writing musical notations
25. Play along with the metronome
26. Understanding tempo and counting the beats in a song
27. Time signatures
28. Odd-time signatures

The most important rule to learn the guitar is: Train 1 Hour Every Day.