Mixing: Using a Reference Track

Most folks would benefit from using a reference track to guide their own mix.
For the uninitiated, a reference track is an existing (pro) song that you use as a comparison to your own mix.
Begin by selecting a song with a similar sound to what you intend to create.
Try to find something as close to the tempo (bpm) of what you are mixing as possible.
Rip a copy from a favorite CD or download a copy from iTunes or Amazon (or wherever).
Add that as a track in your mix.

Needless to say, keep the reference track MUTED as you mix your tracks.
On a regular basis, SOLO the reference track. And see how your mix compares.
Do small segments.
Your DAW should allow you to SOLO the reference track then unsolo to a MUTED state to give a back-and-forth, so you are listen to either your mix or the reference track.

When you are listening to the chorus of your song, shift your reference track so the chorus of it lines up with yours.

Things to pay attention to...

Your Vocal.
Does it fit in your mix the way the vocal in the pro song does?
If you have never done this, you will likely be surprised at how "dull" the pro vocal sounds compared to what you are doing with your own.
Most hobbyist have a tendency to make their vocal too bright - and a bit harsh because of it - because they are focusing on only the vocal and trying to get it "above the mix"...and jacking up the high EQ is the only thing they can think to do.
Most people would benefit from rolling off the really high end and finding other ways to get the vocal in the right place. A bit more compression? of an EQ bump at 1k? A duplicated track with no effects?
Generally there should be a "warmth" to a vocal, but not be "muddy".
It is a balancing act - and the reason there are so many videos about vocal processing.

Drums.
Does your drum levels match your reference track? (Most people mix their drums too low).
Generally, drums should be at a volume level similar to the vocal.

Piano.
Like drums, most people mix their pianos too low. And typically, they are not bright enough.
The BIAB pianos seem to be EQ'd well for a solo piano/vocal mix, but are too "dark" or "heavy" for a big mix, so your mix will get a little "muddy in the middle".
Try dropping out the EQ in the low end and adding a shelf on the high side starting around 2k - then bump that up 3-6 dB...
And make it loud enough to easily hear it.
The piano is a percussive instrument (meaning, like a drum, you "hit" it). If you want pads, use an electric piano or strings or a synth...don't mix your acoustic piano like a pad...

Acoustic guitars.
A lot of people make acoustic guitars too loud in a full mix. They should be "subtle", often "just there" or even "subliminal". Depends on the song, of course, but many people don't pay attention to when they should be more "under the mix".
This likely comes from the fact that acoustic guitar is what they play and what they write with and are accustomed to hearing it all the time.

Harmonies.
Do they sit right for the style of song? Some should be really blended in the background - similar to pads. Some should be like a duet.
Check it against the harmonies in your reference track.

Bass.
Listen to your reference track concentrating on hearing the bass.
Can you hear yours the same way?
That is typically another balancing act between volume and the right EQ.
If you turn your bass up and it makes your mix muddy (heavy bottom) look at your EQ to fix that.

The Chorus.
Does your chorus have the impact that the pro chorus does? If not, think about why. The likely answer is that you do not have enough "helping instruments" to accomplish that sound.