When it comes to learning guitar there are an overwhelming amount of options available to you right from the off. You need to decide what kind of music you want to learn, how formal you'd like your study to be, how much theory based learning you'd like to do and which kind of music you'd like to learn to read. All these choices will undoubtedly make an impact on your playing later-on also its important that you make sure the syllabus you decide on is one that aligns with your goals as a player.
Starting with your goals is the best approach, if you have a clear idea of the outcome that you'd like its much easier to decide which course is going to work best for you. If you are looking to become a professional player or simply looking to learn something to play for your family and friends there's an option out there for you.
Here is a brief and honest outline of the most common syllabuses, exams and courses their strengths, weaknesses and the knowledge they contain.
ABRSM - Classical Guitar - Exams - 1-8 - Classical - If you are looking to become a proficient classical musician which a good knowledge of traditionally written music staff this is the one for you. The Trinity books are well laid out with familiar exam pieces and they have a good emphasis on sight-reading and performance. The wider theory within the first three books is lacking a bit and you won't have an opportunity to cover broader styles of playing but this course presents a very concise and well tested curriculum.
Rockschool Guitar - Contemporary- Exams - 1-8 - Acoustic and Electric - This popular contemporary course is great for player looking to learn the rock and pop styles of guitar. These books are laid out with pieces from different contemporary styles of playing and cover a wide range of genres from jazz to heavy metal. The theory covered in these books is much broader and at the higher levels will cover jazz theory as well as improvisation. The books come complete with both staff music and guitar tablature so a potential pitfall is that Rockschool students may find it difficult when they are presented with just traditional staff in the future (but in the rock and pop world this is unlikely)
Trinity Rock & Pop - Exams - 1-8 - Electric - The Trinity rock and pop series focuses on many of the same elements as its aforementioned counterpart but with a couple of important differences, the Trinity courses exclusively uses well known rock and pop songs which are great for learners that are looking to perform in a band. They also have a good range of genres available keeping the books current but not without their guitar classics!
el Bay Modern Guitar Method - Guitar Book 1-Acoustic and Electric - The Mel Bay guitar method is a fantastic first start to the guitar. It covers all the need-to-know basics in a simple and easy-to-read format. The books in general focus on more contemporary music such as blues and jazz but they use traditional staff so students become adept at reading the treble clef. One of the strongest points about this course is unlike the exam books this book explains the theory as you work through it, every time you learn a new piece you'll learn the theory behind the music which gives you a great contextual knowledge of music theory for guitar.
When it comes to choosing the guitar course that's right for you make sure to examine your goals as a player. Decide what kinds of music you'd like to learn, how deep you want to go with the theory and what your ‘key skills’ are such as sight reading or improvisation. Make sure to look into a couple of different options to determine the right syllabus for you to succeed.