Intro to Mastering

A great book is the Mastering book by Bob Katz.  Its deep and there is a lot to take in.  Many of things mentioned in this video are in this book too.  Mastering is way more than the setup for each song.  There are quite a few other things.
 
1 The balance of the whole mastered sound from song to song.  This can be hard if the final mixes come from all over the place.  e.g. a compilation.  Sometimes you let them be different and not try to mould them too much to an overall sound.  Other times you have to bring some mixes into line.  Easier if all the same studio from the same mix engineer.  It is ultra important while you are mastering one song you must have instant access to the others you have mastered.  For reference.  And fast.  And the very first one you do is also important too.  I choose the biggest track in the bunch. The one that has got everything in it!
 
2 Song order.  This one is quite important.  It changes a lot over the course of a final master often.  It is so important.  What you hear first, then how the ebb and flow goes for the whole project.  Similar tempos and keys not being too close to each other.  It's OK to be quiet for a while (e.g. quieter songs compared to loud ones!) but not too long.  Need to pick things up at some point.  How does it all end?
 
3 Time between tracks.  Slow fade outs don't need as much time to the next track as abrupt endings.  It can seem wrong even when the in-between times are the same.  So you have to tweak some.  Others need more time before the next track hits.  Some tracks less time.  (e.g. very quiet intro)  This is a bit of an art here.
 
4 The level of full on band tracks compared to acoustic tracks with just say one vocal and a guitar or piano.  Or very little instrumentation.  When the rms levels of band tracks and acoustic tracks are all set the same,  (which is good to do and you can master with K System in mind e.g. getting every track to say aK-14 master) the acoustic tracks sound louder than the band tracks and the band tracks then sound whimpy coming in after an acoustic track.  They have to be tweaked here.  I typically drop acoustic tracks down by -2 to -3 dB.  I might even push band tracks up 1 db in overall rms to make them stand out.  Especially coming in after a loud acoustic ending.  Sometimes band tracks can be pushed by 1 dB at the start and drop slowly down to its nominal level over the course of the song. Automation in mastering is a must.  I often automate the loudness of a track the whole way through.  e.g. bring quiet sections up and pulling back some very loud sections.  You need to make these changes silently or without any attention being drawn.  Quite an art here as well.  Tweaking final automation slopes etc..
 
Anyway these are some of the other things you have to think about for sure. 
 
Then there is the old EQ - compressor - limiter combination for each song.  There are tons of options out there and I believe you have select and tweak those as well to suit the tracks you are mastering.  Having a good collection of quality mastering grade plugins allow you to select the right ones for the music.  With all the analog emulation going on too with tape, vinyl, valve signal paths, consoles... etc the options are quite extensive now.  I believe you need a good solid mastering signal chain though to at least begin with.  And a very transparent one at that.  Then you can start swapping things out.  One compressor for another etc... Adding in some more mojo here and there or remaining pristine and true to the source etc..eg a classical master.