Someone may have better advice than me, as I also struggle with it sometimes, but I have noticed I've done better after focusing on frequency ranges while listening. Like, I will focus in on the bass first, and if i'm not hearing a difference there, move to focusing on the highs, and so on. There's probably a better way, but I've found breaking it down like this helps me

I have a strategy similar to Jacob's. I tend to listen to the various instruments and compare them one by one. If i don't hear any differences I move on to the other instruments. Sometimes it's very hard, but eventually I get through.

It has worked for me to pay attention to transients and hi-end. Distortion is a form of compression and the same technique can be applied to Dr. Compressor. Don't be fooled by the level, sometimes the loudest is not the most distorted even if it seems like it. Finally pay attention to the typical scratchy sound of distortion, that ripped sound is usually more present in one take than another. You must consider that of the two takes, one is more distorted than the other, so both will almost always be distorted, and after the 6/8 level the differences are usually almost microscopic!

Thank you all, I will pay attention to those things!