Honestly I haven't read much on say, advertising, and what not, but some for sure (business major, and peruse it here and there). However, what I believe has helped me the most are:
1) Improve my writing / communication skills.
So this involved some reading (good, classic lit, not pop). One person I was just blown away by was James Joyce. Portrait of an Artist as a young man is not overly confusing, but the way he can carry a thought or emotion for pages is hypnotizing. Actually, I also studied Hypnosis. That has affected me the most in my rhetorical style, I'm sure. I used:
http://conversational-hypnosis.com/
^ This is a study Guide. I paid $180 or whatever and listened to all of it (~30 hours). This is the 'go to' guide on hypnosis. I can share the files with you if you'd like.
https://www.youtube.com/watch?v=ja2NEfCEoJk
^ Darin Brown is impressive. Watch the Heist and the Dog Track thing. He's insane.
I also read some Faulkner, Hemingway, etc... but in addition to that, my friend and I started a writing workshop. For this exercise, we'd spend a week on a topic and write a few page story and proof read each others and offer criticisms / corrections. She was already a good writer, but anyways, we both improved dramatically. The idea was not to 'rewrite' but simply start a new thing each week, with the goal of being able to write a solid story on most any subject in a short amount of time (like a few hours), and without revision. Stream of consciousness style writing. Lots and lots of new topics helps to keep you creative, and you'll find the Writing stories is much infinitely easier if you've read lots of stories shortly before.
2) The other thing I've done (and do) is take lots of surveys. For anything like this, I'd do it, show it to 5 people, ask for first impressions and 3 criticisms. What they like about it I usually can tell, but it's hard to know what others dislike. For example, I've found more than 3 prominent colors on a page is bad (eye strain), and that generally speaking the less formatting better. Funky fonts, mixed size text, lots of graphics, etc, are bothersome. Once you caught their attention, a plain typed paragraph is likely as good as any amount of piazzas. All the same, I just take what I got and ask random folk (friends, whatever) too look it over. If their criticisms are different, then I'm probably good, but if 3 ppl say the same thing, it probably should be fixed. That's the way I do it :D
That was fun! :D