First thing I do is hook it up to my SMS-1 and adjust the various settings (phase, FR, etc) to get as flat a response as possible in my room, and make sure that the sub "dissappears" into the room even though it sits right next to the main seat. Once the sub is set up correctly the fun starts.
I have a DTS 5.1 demo disc I love to use with clips from Saving Private Ryan (love the feel of those tanks rolling in), Hotel California by the Eagles, Roy Orbison's Pretty Woman, and some others. I also love to use the scene from LOTR FOTR where Pippin (or whomever) drops the skeleton down the well, some torturous bass starts there! Then off to WOTW and Matrix Revolutions for some more fun!
There are many more (Darla tap, U571, Starwars AOTC, etc) ...
As to what I evaluate, with HT really it's how loud and how low it will go, cleanly (i.e., without chuffing noises or clipping), and whether it gives you that nice "punch" to the chest when it should and cause the room to rumble when required. With music, I prefer tight and fast subs, so that the bass doesn't "hang around" longer than it shouldn't, and the ability to reproduce notes as naturally as possible without sounding boomy.
PBC!