#1
I am on my way to read "The Principles of Correct Practice for Guitar - Jamie Andreas"
People swear by this book, but it really only tells one THE way to practice.
And that in it self is fine. I play acoustic guitar only, but my questions is.
How do I know which areas I need to improve on? Let's say I need to work on Technique, how would I go about that? Should I read this book first, and then apply this to my practice? I often record myself and being self-critic, try to find problem spots I need to work on. But I don't know how in detail, how can I improve? Is practice only learning new songs, to perfection?

Could anyone please help me?
#2
Read the book first, then worry about applying it. It provides some guidelines itself.


How do I know which areas I need to improve on? Let's say I need to work on Technique, how would I go about that? Should I read this book first, and then apply this to my practice? I often record myself and being self-critic, try to find problem spots I need to work on. But I don't know how in detail, how can I improve? Is practice only learning new songs, to perfection?

Could anyone please help me?


Not really. Almost all of your questions can be answered with "it depends". You have to prioritise areas of your playing based on your desires and your problems. Then practice accordingly.