New monitors? Now you need to tune in your ears.
I wrote recently why your studio monitors should not make your mixes sound great. They should allow you to hear any defects more clearly and help you achieve a balance that will sound good on any listening system.
But there is another important point. If you buy new monitors, which presumably will be better and more expensive than your old pair, then you need to learn how to use them.
If your new monitors were perfect, then perhaps you could just start mixing straight away. But there is no such thing as the perfect loudspeaker. All loudspeakers have their own characteristics and divergences from perfection.
So what you need to do is learn how to compensate for whatever characteristics and defects your monitors have. For this you need first-class reference audio material. If you have audio references of unimpeachable quality, then you can listen carefully and judge how they sound on your new monitors. You can do this even if you don't intend changing your studio setup. And in fact you should do this whenever you change anything in your studio that will affect how your mixes sound to your ears (and hence to your audience).
Sources of first-class audio reference material
The question now is where do you find examples of audio that are truly and incontrovertibly first class? There could be a number of answers to this question, but I will concentrate on four...
1. The artist or band that you would like to emulate
That's an easy choice. You probably don't want to sound exactly like your heroes, but a range of material in the genre or style in which you work will be very suitable for this task.
2. The Bob Katz Honor Roll
Bob Katz is a mastering engineer whose work has been revered for decades. He has compiled a list - his Honor Roll of albums that sound great, and are, according to Katz, "some of the best-sounding popular CDs ever made". It has to be said that this list fails to include recent music releases, but if you check out the link then you will see why this is so.
3. The Billboard charts
This is perhaps obvious, but if you want your music to be successful, then absorbing the sounds of the currently best-selling music will surely be a good thing. Billboard charts, in their various genres, are probably the most significant worldwide, but you may prefer to use the major charts of your own country or region.
4. The Grammy awards
This must be the ultimate reference point. It would be great to make recordings that are as good as those that are commercially successful, but to be as good as nominees and winners of Grammy awards is the icing on the cake. There are of course other awards for outstanding achievements in music, but the Grammys are definitely the most widely respected.
How to use reference material
Now that you have sources of reference material you need to know how to use them.
Firstly, you need this material on CD. Compact Disc might be seen as a format that is on the way out, but it is the format where you will get the best sound quality. Streaming and download formats that use MP3, AAC or OGG are lossy formats that reduce the data of the original recording down to a small fraction of its original detail. CD, with its 44.1 kHz / 16-bit resolution is as close is it is commonly possible to get to the original master's 44.1 kHz / 24-bit or perhaps 96 kHz / 24-bit format. If you can find a WAV file download that is better than CD resolution then you should use that.
Once you have your reference material ready to play, you should immerse yourself in the music. Sit in your producer's chair and listen intently, at a range of volume levels. Stand up, walk around the room. Get to know how this music sounds at every location in your studio. Stand outside and listen to how much bass comes through the door. You might even gently touch the woofer and feel how much it moves. All of this will add to your experience of how music should sound in your studio. Then you can work towards making your own music sound like that.
In summary, your monitors should allow you to hear any defects in your mixes and help you focus your efforts towards the perfect mix. Your experience of listening to mixes that have a proven record of success will help you achieve a similar quality of sound in your own work.
P.S. For an alternative take on this topic, you might consider the voice of the people...