​Knowing your intervals helps you quickly find the roots of classic chord progressions.  Since many chord progressions in classic jazz tunes move in fourths, it is a good idea to learn the circle of fourths and be able to move in fourths at any point on the guitar neck.  This pdf might help you locate all the perfect intervals in the major scale.

​Since the guitar is stacked in fourths, moving vertically from bottom string to top is automatically a fourths motion.  In the image below you can see how starting on the third on the low E and traveling to the high E will move you though the roots of a 3-6-2-5-1 and then to the four.  Remember that strings 2 and 1 (B and E) are tonally shifted up a fret.  The vii happens to be a tri-tone away from the IV. Tri-tones are basically a 'diagonal' away on the fretboard.

​
You can see how a 3-6-2-5-1 would look on the circle of fourths below.  Moving in a counter-clockwise motion brings you from the iii around to the I and then to the IV if you continue.  In order to get to the remaining interval -- the vii -- you would have to jump to the other side of the circle. Diametrically opposite tones on the circle are a tritone apart. 

It is essential at some point to be able to visualize your intervals across the fretboard given a root note.  In learning this, I quickly realize that, unless the notes are separated by the string shift at the B-string, the 5 always sits over the Root, the b7 always sits over the b3, the Root always sits over the 11, etc.

After that, I began to realize that since traditional positions move in fourths, and the guitar is more-or-less tuned in fourths, the 3-6-2-5-1 sit on each other vertically.

Here is the complete vertical layout of the intervals following this concept.  Maybe it will help you learn the intervals, or at least be able to quickly double-check.

The second page in the pdf has worksheets where you can fill in the intervals.  It's not necessary to have these worksheets to practice.  You can scribble out a 7x7 grid anywhere.  When you fill out the worksheet, try and fill the boxes as randomly as possible to help you learn where things are.