Hey,
I like that you put this out there to comment and share your practice. I want to give you some valuable input so I managed to find and download the multitrack and I am currently doing a quick mix myself, in order for me to better understand what you had to deal with. It will also allow you to give credit (or not) to my advice, because obviously if you don't like what I did with the song you shouldn't follow it.
First, I'll mention that in my opinion the recording engineer / producer did a somewhat sloppy job:
* The kick track has been recorded too hot and is distorted all the way through.
* The snare doesn't sound great, it lacks a bit of body and has too much ringing sustain, it should have been tuned properly and maybe use some moongel or something to tame this very obvious harmonic ringing.
* The drums have been edited for timing, but some cuts are a bit too obvious. There's not much we can do about that at this stage.
* The electric guitar tone is very dull, I can't believe no one did something about that at the recording stage. There are some drastic EQ corrections to apply here at the very least.
* The vocals have been edited too and some cuts are quite obvious since they happen during the breaths. Fortunately this is an easy fix. However, the very last line is recorded with a loudspeaker on or something, there is a lot of instrument spill in the vocal track at this point.
I hope I'm not offending anyone, in case you know the artist or producer. I'm just mentioning what I am hearing because I think it is important since we're practicing mixing here. And I'll also say that the vocals are often out of tune, but I noticed that you have corrected the most obvious strayings here.
I'll post my own mix and comments on yours shortly, probably tomorrow.