Get a good resource book that covers all aspects of chicken care. Read it, then read it again. And then possibly a third time, at least the parts on care and maintenance. Then spend some time perusing this forum. Feeding, coop/run, care, etc. are all general information topics that are covered ad nauseum in a multitude of places. And for the most part, the information doesn't change. All chicks and layers need the same things regardless of who owns them or where they live.
From the BTDT practical experience standpoint, from my limited time owning chickens: observe your chickens daily, preferably multiple times a day. Most of time you won't have a problem. But if you do, part of being able to tell you have a problem is knowing what is normal behavior and what isn't.
Example: last weekend my husband--who pays very little attention to them--came inside and said I needed to go out and check on of the girls. She was hunkered down under the coop, almost like she was sleeping. So I go to the run. Upon seeing me, she hops out and comes over expecting a treat. You see, my husband didn't know that under the coop is their favorite afternoon napping spot. They've even scratched out some divots for themselves. It was completely normal behavior for them.
But. Here's why it caught his eye. About six weeks ago when the weather was still cold enough at night for me to shut them in the coop, I went out to do it, following the normal routine of a head count before latching the coop door. Only this time I kept coming up with 4 instead of 5. It's a small coop, and the roost bar is high up making it difficult for me to see all of them when they are on it. I counted 4 or 5 times, even tried counting feet, but still kept coming up one short. Fearing the worst, I checked under the coop. There was my fifth girl, sprawled out on her side dead. I do not know why she died, but my best guess is egg bound.
To drive the point home about knowing your chickens' behaviors: this was the first day in a long time I hadn't checked on them all day. I saw them in the morning when I fed and watered them, and once in the afternoon, but that was a cursory look just to make sure there were 5 chickens. Not really a good look at how they were behaving. And a good 6 hours between that look and when i did the head count.
Had I stopped to take a look, or looked more often that day like I normally do, I might have noticed behavior from her that indicated a problem. I was hampered additionally by the fact that they were still in winter laying mode; I was getting only about 2 eggs a day from the 5 of them. And I have never been able to tell who is laying when, or what eggs. So I didn't have the benefit of realizing that "hey, laying is off a little here" that I would get in the summer when laying is going full steam ahead. She was never exhibiting any other symptoms though. That's part of the reason I assume egg bound. Though it could have been just about anything (except predation).
I don't know that I would have been able to save her had I been keeping a closer eye on her. But I definitely couldn't fix what I didn't see/notice.
Those are just two anecdotes that illustrate why it's important to know your chickens by their behavior. Mine aren't pets and they only come around because they think they might get treats. But I still know who the low chicken on the pecking pole is. I know who the curious one is. I know who the laid back napper is. I know who is the most aggressive at feeding/treat times.
It should go without saying, but I'll say it anyway, part of observing their behavior means observing their physical appearance as well, taking note of any changes that might indicate something is amiss.