A very important thing is to have a good grasp of intervals and scale shapes on the fretboard. Knowing intervals as they apply to guitar will open up your playing so much more. For example the interval of a perfect fifth (7 semitones), or a major third (4 semitones), or a minor third (3 semitones). And despite what some people say, learning scale shapes is very useful, as long as you know the theory behind them, and be able to use them musically.
Picking any note on the fretboard, say the low open E, and playing the fifth with it (B) creates the common power chord, or fifth chord, which would be notated as E5. In this case, the notes of our E power chord are: E B. It doesn't matter where these two notes are played together on the fretboard, as long as they are played at the same time, they will sound an E5 chord. You can also arpeggiate the chord, and play the two notes separately.
But the principle of notes sounding together applies to all chords. If you have a major chord, say C major C E G, ANYWHERE you play any combination of these three notes, you will be playing a C major chord. With that in mind, different combinations and ways to play a chord are referred to as voicings. Here is where it really gets interesting: Say you are playing in the key of C. On any 3 adjacent strings, you have 3 different possible "inversions" of every triad that you play. This means that on the G, B, E strings, you can play a C major three basic ways:
This is a regular C major.
Note that the bass note is C, and the treble note is G, and all three notes are in the standard C major chord order: C E G.
Now this is a C major in first inversion.
Note that the C has moved from being the bass note to being the treble note, and E (its third) has become the bass note. C E G -> E G C
And this is a C major in second inversion.
The bass note is again moved to being the treble note, and G (its fifth) becomes the bass note. E G C -> G C E (note how the C is in the middle and is the least resonant note in this particular voicing)
If you play these three inversions of C, you will probably realize they have a distinct sound from one another. Why? Well, the bass and treble notes are the most audible notes of a chord, and the middle note is less noticeable to the ear. So when you play a standard C E G, the two strongest notes are C and G, which together form a nice and stable C5 power chord.
Now looking at the first inversion, the bass and treble notes are E C. This is the root, C, and its major third, E, which gives this chord a really "major" feel, because the two strongest notes together form a major third interval. Since a major third sounds different from a perfect fifth like in a standard C chord, it will give this voicing a different sound.
Now for the second inversion. It almost doesn't even sound like a C major... Well it is, but by looking at the bass and treble notes: E G, and using all that theory that you know, you can see that they are a minor third apart, as in the chord E minor (E G B). In a C major in second inversion, the root, C is sandwiched in between two notes that together form a minor third, giving this voicing a kind of "sad" minor feel.
Now this concept applies to any three adjacent strings, for any kind of chord, and in any key. Start playing and experiment with any chord, be it minor, major, diminished, or augmented, or anything, and play it in different places on the fretboard and note how they all sound. It's pretty overwhelming when you think about how many chord possibilities there are, even in one key.
Now you can even piece together these triads to form 5 or 6 string chords all over the fretboard. For example C major:
C major on the A, D, G strings
You can play these chords partially, as a whole, arpeggiate them, add in other notes or alter the quality of the chord (make it minor or diminished) or use them in whatever way you want to in order to get an interesting sound.
So how does all of this help your playing?
Well now you can be more mindful of your playing. It should be easier to figure out many different voicings of chords that you can use to make your playing more interesting. Eventually you will be able to improvise much better, and know what you're playing while you're playing it. Pick a key, like C major, and start improvising slowly, but really think about what chords and notes you're playing, and you will notice that eventually you will be able to navigate around the entire fretboard much easier. When you start getting bored of diatonic chords, throw in some chords from the parallel minor (C minor) or other keys and experiment!
Hope that this made sense, and will help you improve your playing by being able to apply the theory you know to the guitar.