5 Positions of major Scale

According to CAGED guitar system, there are 5 positions of major scales on guitar.......
E 

D
This is sometimes referred to as the Dorian position because the lowest note is the second scale degree - but you're going to start on the root note and hear it as the Major scale, aren't you? :).
* - this note should use the 4th finger when the scale is descending and the 3rd finger when it is ascending. I believe this is the best fingering and keeps you hand in the best position.
Alternatives
The most common alternative is to move the two notes behind the root (strings 3/4, played with first finger) to strings 5/4 and playing them with the little finger. I don't see this as a bad way of doing it but this way the third of the chord is closer to the chord shape (which is how I see scales).

C
This is sometimes referred to as the Phrygian position because the lowest note is the third scale degree

A
Don't forget to start on the root note, not the lowest note...
Alternatives
The most common alternative is to move the last note on the second string (played with 4th finger) to the first string (then played with 1st finger). I prefer this position because it is very common to add that note (it is the 4th degree of the scale) to make a suspended sound and this is the place where you would add it.
Other alternative is to add a high B note to the top of the scale, but then it becomes a 3NPS (Notes Per String) scale which is another system that we are not doing here...

G

This is sometimes referred to as the Aeolian position because the lowest note is the sixth scale degree - but you're going to start on the root note and hear it as the Major scale, aren't you? :).
* - this note should use the 4th finger when the scale is descending and the 3rd finger when it is ascending. I believe this is the best fingering and keeps you hand in the best position.
Alternatives
The most common alternative is to move the note behind the root (strings 3, played with first finger) to strings 4 and playing it with the 4th finger. I don't see this as a bad way of doing it but this way there is a consistent method to fingering the scales - in relation to the other shapes above.