Plagal Modes are used in a different way than the Authentic Modes.
They have a lower range and for that reason they are written in the clef of C.
Two notes are important the Final and the Dominant.
The Final and the Dominant in the Plagal Modes are different than those in the Authentic Modes.
When using Plagal Modes you MUST resolve to the Final.
They have a relative Authentic mode. But by accentuating the Final and the Dominant of the Plagal mode you create a particular "Mood". and as a result the tonality of your music is changed.
For comparison reasons I`ll writte the modes, using darker letters for the Finals and Dominants.
"D aeolian"=[D-E-F-G-A-Bb-C-D]
"D dorian"=[D-E-F-G-A-B-C-D]
"D hypodorian"[A-B-C-D-E-F-G-A]
"A aeolian"=[A-B-C-D-E-F-G-A]
Note that the three first modes are to be played over a (Dm) or (Dm7),
and the last over (Am) or (Am7).
Some books to read are:
-"A handbook of Modal Counterpoint"
-The Style of "Palestrina and the Dissonance"
-"Sixteenth-Century Polyphony"
-"Contrapuntal Technique in the Sixteenth Century"
-"Approach to Counterpoint in the 16th Century Style"
Websites:
http://clem.mscd.edu/~yarrowp/MODEXh.html

If you are not intersted in the theory I`m gonna post a tablature of a lick based on one of those modes.