Watch the II - V - IV - I Dorian online guitar lesson by Robbie Calvo from Modal Expose
In the opening line of this solo sample I wanted to introduce the characteristic note of the Dorian mode, the major 6th. In this case the G#. I'm focusing my resolutions to F#, the 5th of B minor 7 and the E, the root note of the E9 chord. These are very simple lines but I always target the chord tones.
You'll notice my ideas are often derived from specific arpeggio shapes because they give me certain lines and places of resolution. For example the B minor 7 arpeggio lines at the 2nd fret. Of course you could also see these ideas as minor pentatonic lines too because B minor pentatonic is a B minor 7 arpeggio with and added 4th.
The most important thing to remember here though is that this is a Dorian progression and that means we are focusing our tones towards the resolution of the II chord, B minor 7. If you want to accentuate the Dorian sound, try playing the G# more often in your lines but remembering that G# is not a chord tone or resolution point, okay?! - it's the characteristic note of the mode and it's your choice whether or not you use it or like how it sounds. Don't let the Purists tell you otherwise!