HOW TO know your fretboard

Knowing the fretboard is important because each fret on each string represents a specific note. In the diagram below, you will notice that I've only labeled the 6th and 5th string, up to the 7th fret. The reason for this is because in my opinion, knowing these frets well is essential for knowing how to play chords. I will further explain.
As you can see from above, the diagram represents the fretboard. The letters on the right represents the tuning of each string, which is EADGBE (standard tuning). Next, the numbers above are the frets (I've labeled till the 7th fret), and the letters in the fretboard are the notes, if you play on that fret.

Note: If you play the 6th string 1st fret, you're playing an F note. You don't have to put your finger on the fret (the metal bar) itself, as long as your finger is in the white space from the nut to the 1st fret, it is an F note.

Figuring out Chords
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You might ask the question, "Why is it important to know your fretboard?". Let me explain (with regards to playing an acoustic). To me, knowing your fretboard is important for playing barre chords and figuring out chords. I will not go into detail in this post, but if you know your fretboard, you can play every chord with just the barre chord pattern. More will be explained in a separate post.

Knowing which bass notes to play
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When you play chords, you have to also remember that not every chord requires you to strum all 6 strings. Let me give you some examples. If you play a G chord, you strum all 6 strings because your middle finger is on the 3rd fret of the 6th string (G note). If you play a standard C chord, you strum from the 5th string down because your ring finger is on the 3rd fret of the 5th string (C note). If you play a standard A chord, you strum from the 5th string down because the 5th string (free) is an A note. If you play a D chord, you strum from the 4th string down because the 4th string (free) is a D note. The same goes for an E chord. You strum all 6 strings because the 6th string (free) is an E note.

One more note about the labeling of notes. Some of you might ask, if there's a Bb (B flat), why isn't there any Gb or Ab etc. Well, these notes do exist, and to simply put it, it is interchangeable with the sharps. Let me give you some examples. You see on the 2nd fret an F# note. This note can also be known as a Gb. This is because when you move UP a fret from the F note, it moves a semi-tone, so it goes to F# (2nd fret). When you move DOWN from the G note, you are moving a semi-tone down, so you say Gb.

Note: Notice from E to F, and from B to C, there are no sharps/flats. There's probably an explaination for this, but I have to admit, I don't know either. It's just the way it is.