Hey Friend,
In the key of C major, we've established the IIm chord is D minor.
Now here's the thing about using Dm in a progression (or any IIm chord, for that matter). If you're sitting there scratching your head saying "What the heck is this 'IIm' thing he keeps referring to?," here's a refresher...
We use Roman numerals to denote chords from the key. Traditionally, we'd use upper and lower case to specify whether a chord was major or minor, like this:
I ii iii IV V vi vii°
That method seemed to run into some conflicts with other notation, so it was modified to only use capital Roman numerals with an 'm' to denote when a chord is minor. Like this:
I IIm IIIm IV V VIm VII°
I've seen this called the Berklee School of Music method, part Nashville numbering and part classic notation. Pick your poison. I'll use this way to try and keep things clear.
When we play Rock songs, the IIm chord doesn't come into play very often. Most of the time, we end up playing the I, IV, V and VIm chords. IIIm comes in handy at times, too.
Where you might find a IIm chord could be in a bridge section of a song, but frankly, finding an example in Rock is a real challenge.
However, If you like Jazz music, you will find the IIm chord used quite a bit more. For instance, a very common progression is IIm, V, I.
I find there's not that much tension between the I and IIm chord - yes, there is some; that's the nature of major/minor chord combinations. But to use them in a progression right next to each other? Not so much.
Given we've only covered the C major and D minor chord from the key of C major so far, we don't really have much to work with when creating cool progressions. I've tabbed some simple chord changes you can practice (and this is always good practice).
Notice how you can simply lift your index and middle fingers and shift them over by one string. This is a fairly efficient chord change because you maintain your fingering shape for two notes. Too bad we won't be using this progression much!
On the other hand, practicing this chord change prepares you for others we WILL use in the future, so don't skimp on this one.
Until tomorrow...
Peace~
Dave | 
