The way I see it, modes are just variations of a 7-string master pattern that have different beginning points. Below is an image of this master pattern. Note that the bottom three lines are the same pattern, the 3rd and 4th lines are the same pattern, and the 1st and 2nd lines are the same pattern. These groupings of fingerings form the basis of the Modes.
The black lines (first 6) above make up what is called the Major scale as played on a typical 6-string guitar. The root note for this scale is the first note on the 6th string. Below is a modified diagram showing the Major scale on just six strings.
In the master pattern at top, again notice that the bottom three lines (including blue) have the same fingering pattern. As noted, the Major scale (Ionian Mode) fingering pattern begins with the first note of the second of the three similar lines. So what do we have if we shift our master pattern up so that the root note on our 6th string corresponds to the first note of the third of these three lines? Answer: the Mixolydian Mode.
And if we shift our master pattern down so that the root note on our 6th string corresponds to the first note of the first of these three lines? Lydian Mode
I hope that you can see that the fingering groupings are the same for these three modes. All that is different is where in the master pattern you choose to begin with your root note (well, that and the shift thing on the top two strings--see the noodle stuff at bottom of page). The master pattern is behind all of them.
I've laid out all of the modes in a pleasing pdf file that you can see and print by clicking the image below.
Wanna fry your noodle?
The modes above all start with the root note on the sixth string of your guitar. Did you notice that the root note is shown as a square? Do you see other squares in the mode patterns? Those are the root note again, appearing octaves apart from the starting one on string six. Any one of those square notes can be used as the starting point for the mode pattern. Except now, instead of only being able to "walk up" the strings from six to one, you can walk up and down the strings in the same mode pattern from any string anywhere on the neck.
Be aware that there is still that "7th string" to account for when you are wrapping your fingering patterns around the fretboard. Notice in the Lydian example above that the first string and the sixth string have the same fingering pattern. This is because what you see on the first string is actually the wraparound of the blue seventh string seen in the master pattern example. The middle of the three bottom lines from the master pattern is "in limbo" so to speak behind the fretboard.
Note also that the nature of guitar tuning dictates that the top two strings are shifted one fret to the right from the rest of the strings. If this were not so, the master plan's top two lines' pattern would sit directly above the 2nd and 3rd lines' pattern. It would be so much easier to remember that way. But is not like that and those top two lines do shift one fret to the right. So, every mode/scale will be a little different as each will have a different set of two strings that need to shift.
A cool exercise is to play one mode up from the 6th string to the 1st string, then slide up/down one note and play the adjacent mode down from the 1st string to the 6th. Then slide again and play the next mode up, then slide, and play the next mode down. Again, and again, and again.
