Firstly, I'd like to say that i'm not a guitar teacher or a theory expert for that matter, but I would like to say that what I am about to talk about hugely helped me trying to learn the fretboard and also a few of my friends.
So I thought F*** it! I'll give it a try sharing a few of those ideas with you guys.
Right, the main step in any form of music theory in my opinion is to tackle it from different angles. Its when you're brain starts to make little connections between them you start to know things on auto-pilot without really having to think about them at all.
For learning the fretboard I found countless approaches on how to learn what notes are where however, I found it was only when I constructed a routine which involved multiple approaches it all started to sink in.
Here is a short list of the little tricks or methods of learning the guitar fretboard I found worked really well once I started to use them all together in a constructed routine...
Learning the major scale on one string. Counting forwards from an open string to the 12th fret, then counting back downwards to the open again.
After a little while you will notice where some of these notes are. Once you are fairly comfortable move onto another string and do the same thing until you have covered all six strings.
(If you don't know how to build up a Major scale just ask me.)
Learning a single note on every string. For example finding the C on the low E string (which is on the 8th fret) and then on the next string (A string) by just hearing out for the note that sounds the same as the C on the low E string. Once you get it, make a mental note of what note it was and move on to the next string until you have finished every string. Then when you are comfortable with that note, move onto another note. (Don't push to hard with this, try and learn a note a day on all strings, then just keep testing yourself until you are fluent at finding the notes on different strings.)
Honestly, its great. And there is a sense of achievement watching yourself get better and better each day! As well as using this application you should also try and do it on you're own guitar with somebody (that's a tad patient) just calling out random notes. It does work but don't just rely on it! Use it in a routine (otherwise it is pointless).
Diagrams! draw out a picture of an empty guitar fretboard (like yours), Draw in where the inlays should be and refrain from numbering the frets! And just fill in all the notes, first you might want to try doing the major scale in order on each string. Then maybe you might want to do method 2, just do it all note by note on all of the strings. There is so many different ways you can do this I am just trying to share a few ideas.
Play the tunes you already know! Just when you do, take it slow and look where you're fingers are and try and think of what notes you're hitting each time. You'll start off slow but you will notice great improvement over time! Just like with what I've said with the other methods though, don't rely on it! Use multiple methods.
Hum to yourself the same tone of the notes that you are playing, this may seem pathetic and silly but it is probably one of the most fundamental things you can be doing. Developing you're ear. And the earlier you start, the faster you can get used to knowing what notes you are hearing in your head, and channel them through to the guitar (without having to count back from the 12th fret)!
This process probably does take the longest, but the more and more you learn about the notes you're actually playing, the easier it gets.
Right... that's enough from what I can give you to work on. The main point is that you rotate different exercises and methods to really "unlock the fretboard" and see each fret as a note and not a number.
Try to construct a dedicated routine for yourself, and stick to it! and by all means don't use just the methods I pointed out above, try to create you're own! Just make it realistic to your playing abilities, set yourself goals, and stay dedicated! Once you get past the early stages of learning it wont seem anywhere near as confusing.
A quick example of one of my days exercise plans for learning the fretboard:
20 mins Method 1
20 mins Method 2
5 mins Method 3
20 mins Method 4
And then the next day I would practice using the different methods OR just do the same but in a different order. Like I keep saying, make your own methods!
Thanks for taking the time to read this, like I said at the start, I have never made a lesson on UG before. Nor am I the best teacher in the world. However I thought that keeping a routine like this worked better than any other singular method.
If it is confusing at all and you don't really understand anything in particular, please feel free to ask me. I will do my best to help.