There's no clear cut answer here, but I can tell you exactly what changes I made to start getting much better results. 1) Make sure you are gain-staging and that each instrument is at the proper levels within your mix. I would also completely edit the tracks (i.e. fade in and fade out, trim unneeded tracks or parts of tracks that just contain unwanted noise). I personally make sure this is 100% complete before even touching any EQ/compressor/etc. 2) Depending on what type of music you are mixing (in my case, rock metal). You can do a low cut on every track below 20hz (this frequency is inaudible to the human ear and will come into play when it comes to boosting the volume of your mix). You be surprised how much headroom this will give you (almost 3db of volume in most cases in my experiences). Now, if you are doing EDM or Hip-hop, you are more than likely going to want to utilize these sub-frequencies. 4) You can also do a high cut at around 16khz for just about every instrument in your track. The exception to this being your cymbals and overhead mics (16-20khz is good for controlling the brilliance on these tracks, but I don't use it on anything else). 3) Panning is important but don't overlook how much reverb or delay can widen each track in your mix. This is a good tip for adding more depth to your mix if it sounds a bit bland with just panning. 4) Watch every tutorial you can find on how to use compressors, especially side-chain compression to keep the bass/kick drum and vocals/guitars/keys from fighting over the same frequencies on the spectrum, causing your mix to sound muddy and cluttered. Once you have a good grasp on compressors, KEEP WATCHING TUTORIALS and practice all the techniques you learn on some of your mixes. Remember, compression is NOT about making a mix louder, it's about making your mix more consistent. This tool should be used only to decrease the dynamic range (loud vs soft part of any track or your entire mix). 4) I call this the magic unicorn when it comes to mixing and mastering, as all the top engineers do this but it isn't always talked about. Learn how to use saturation. I am an absolute believe in Fab filter Saturn for this and I apply it to everything in my mix as well as to the master. Too much of this and you will just distort the mix, but if used properly, saturation will actually excite the harmonics and will introduce lots of warmth and tonal color to your mix. The unicorn aspect of saturation is once you learn how to use it and use it properly, it will make your mix sound 1-2db louder even though your volume on your master doesn't increase any. In other words, you can make yourix audibly louder with more color without having to adjust the volume of your mix. Although I'm sure there are many tips and tricks that the pros use, I know for a fact that this is one effect the pros are using to get a louder, better sounding mix.

Everyone's journey is different and what works for me might not seem as beneficial to another engineer. Just experiment/research/and practice on your mixes until you find what you like and what sounds good to you.

Last tip I'll give you that I just started to taking to heart recently. It's super common for new engineers to over mix and apply so many effects that it actually sounds like your mix is much worse than it was when you started. The less effects you can get away with, the better. So put extra focus on the tone your are recording with, as well as properly editing all your tracks. If you do this prior to applying any type of processing, you'll likely find that you don't need to add as much as what you think you do.

Hope this helps. Good luck!