How do you compare components?

When comparing differences that are subtle, I listen to stuff I know well, and take my time to overcome the day-to-day variables.  Sometimes characteristics start to show up that I didn't notice immediately. and sometimes it's things I can't "unhear".  Once you've got a feel for each, go back and forth and confirm which one you like best.

Make sure you level match using a decent spl meter; otherwise, the loudest thing wins. 

Good advice from @ghdprentice. I have a minimum three day rule on making any conclusions on new cables, but in reality it is much longer. Sometimes the differences are clear and you can put it into words. Other times, at least for me, there is just that gut feeling that you prefer one over the other. I would listen to the cheapest for a baseline, then go top down.

@whart 's comment needs to be at the top.
This is the single most important thing when comparing components.

I use a white noise test tone and adjust the level to 81dB at my listening position. I prefer to do critical listening at pretty high volume.

I have a list of songs I use. 
I strongly suggest you do not rely on strictly "good" recordings. For instance, one of my tracks is Low Spark of High Healed Boys by Traffic. The album is terribly recorded and can sound horrible on a very revealing system. If this sound sounds unlistenable on your system, then maybe you are not listening to the music, but the gear.  
Another track I use is Voodoo by Godsmack. If your system has issues with low end, this track will reveal it.
After that, I really like to use metso-soprano vocals and male choir for midrange. 

Use music you have listened to for years. Stuff that you know every tiny wrinkle.

Lastly, do not expect anything. I do not hear any appreciable difference between HDMI cables that are actually certified (most are not). In fact, I went back to USB input to my DAC because I thought it sounded better than the i2s input. YMMV. 

Excellent advice all. Thank you for your input. I definitely have a plan now. Will report back.