What I look at is typically
1-comb type
2-random traits like muffs, beard, feathered legs etc
3-skin color
4-variety (feather pattern)
5-earlobe color
6-body type
6-egg color
7-sometimes eye color
While yes, there are many varieties within individual breeds, most birds shown on here are hatchery birds. A huge majority of owners buy from hatcheries and these hatcheries carry maybe 100 different breed/variety combos.
One problem when getting better at individual varieties is the weird variation in lingo. Execheur and mottled are both the same, same with paint and erminette, the whole European vs American definition of what partridge means among others. Every APA recognized Brahma variety is actually a different name for another variety (buff=buff columbian, dark=silver pencilled, light=columbian). There is so much nuance once you start to understand varieties.
What I would start with at first is knowing comb types by heart, single, rose, walnut, cushion, pea, v, and carnation will probably be the only commonly encountered ones. Then, just scroll through hatchery websites of the more common ones like Hoover's and Meyer. If you know all of these and their traits, you'll know most every chicken you encounter. I adore books like Pocketful of Poultry and Storey's Illustrated Guide to Poultry Breeds both by Carol Ekarius. They're awesome books and help you learn the possible varieties for each breed. Learning all of this, while amazing and I recommend just to better understand the breeds themselves and to be able to know about their histories a bit too, isn't really applicable to determining most commonly encountered breeds. Anconas, Dorkings, Rhode Island Reds, and Leghorns all come in rose comb varieties (despite most people thinking they're only found in single combs) and yet I have never seen someone just stumble upon one because they're pretty uncommon.
One thing that really helps me that I don't really see being mentioned is knowing the APA class of each breed. It's debatably unnecessary to know, but there are some cool correlations between class and breed traits. I won't go into it a ton, but if you really want to get unto grasping breeds, knowing their histories is vital and *typically* the class name corresponds to where the breed is from. For example, most breeds in the "American" class have yellow skin and most in the "continental" and "English" class have white skin. The continental class describes breeds from Northern Europe, English class describes breeds from the UK and the American class birds from North America! Even if you don't know a breed, by seeing the patterns within a class, you can get a clue at it's origin! I'll stop rambling now, but I find chicken breeds so fascinating!
