Blues Progression

I've been trying to write a blues rock style progression, and I hear a lot of people saying you play the root chord, then the 4 chord and the a whole step up from that..not entirely sure what they're talking about and I was wondering if someone could expand on this. How would I write a progression in the Key of D for example. Thank you.

Improving Rhythm Guitar

I have been looking to improve my rhythm guitar playing (preferably rock blues), I know the traditional open chords, barre chords etc. But I've been looking for a way to move around the fret board more. Spice things up a bit but keep a nice hard rock or rock blues sound.

Major Scale Improv

Ive been trying to work on my lead solo improvisation skills, and a HUGE influence of mine is C.C Deville from Poison, i love his playing technique. I was wondering when im playing in a major progression..how do i know which mode too start playing in...also..how do I figure out which chords make up a scale ...:s