Originally Posted by: shapertakhf#m Dmaj F#m Emaj ...[/quote]
Write down all the notes in all those chords:

F#min - f#, a, c#
E maj - e, g#, b
D maj - d, f#, a

Write them linearly:

f#, g#, a, b, c#, d, e, f#

This does yield the F-sharp minor scale! But since the D major scale has a "g" as it's 4th and not a "g#" it can't be the D major scale.
[QUOTE=shapertakh]if its the key of f# then how do i associate this scale/mode with its tonic D scale????

The relative major of F-sharp minor in A major. Consider this: the notes that make up the A major scale and the F-sharp minor scale contain the same notes. The only difference is which one gets labelled scale degree number 1 or the tonic.

A major:

a - 1st
b - 2nd
c# - 3rd
d - 4th
e - 5th
f# - 6th
g# - 7th
a - 1st

F-sharp minor:

f# - 1st
g# - 2nd
a - 3rd
b - 4th
c# - 5th
d - 6th
e - 7th
f# - 1st

Going back to your original chord group:
F#min - f#, a, c#
E maj - e, g#, b
D maj - d, f#, a

The big clue in that group is the two major chords a whole step apart: D major and E major. The only place you find two major chords a whole step apart in natural major is between the 4th and 5th. The only place you find two major chords a whole step apart in natural minor is between the 6th and 7th.

Also check out my Modes tutorial: http://www.guitartricks.com/tutorial.php?input=370

Hope this helps.