Hey man. Equalizing is a must for electronic production. It is one of the biggest, if not the biggest aspect of mixing and balancing. It's all about training your ear. The more you do it the more familiar you become with sound; how it resonates, what to look for, how to get rid of disturbances etc etc.
It's about experimenting, getting familiar with the hearable Hz's, and knowing how your equalizer works. A proper mix is a mix that can be played loudly without disturbances/edges - but keeping a profound or powerful appearance.
It's also about testing your sound on a variety of speakers/headphones etc, for reflective purposes. A good mix reacts well on most sound systems.
For a part equalizing is taste. But there are certainly guidelines that everyone follows to get stuff done.
I have blogged about the basics of mixing/balancing. If you're new to this all, have a look (it's mainly written for starters). The following episode is about equalizing (I am not aware of any rules against linking on this forum, if so, my apologies): https://typhonicsamples.com/music-production-ep-4-pain-borders-and-sweet-spots/