You need to get yourself some basic/core books on card magic and learn the foundations. That's where you'll find the basic answers to your questions. Royal Road to Card Magic... Expert Card Technique... Card College... you'll find what you need to know there. Even something as "entry level" as Mark Wilson's Complete Course in Magic contains basic false shuffles that can be used to position a card where you want it.
For a comprehensive "visual" reference, get Daryl's "Encyclopedia of Card Sleights" DVD set. You'll have more than enough false cuts and shuffles to keep you busy for a while.
As to what's "natural" with respect to card handling, this is sort of an ongoing debate in magic. Some argue that your card handling should resemble the card-handling of a layman as much as possible; others argue that laymen expect magicians to handle cards differently than they do, so why deny that expectation if you want to be perceived as a magician? Others argue that it really doesn't make any difference. I say it depends on how you want to be perceived.
Different people handle cards in different ways. Some laymen handle cards differently than other laymen. Magicians handle cards differently than laymen. Gamblers handle cards differently than magicians. Do you want to look like someone with great skill with cards or just a guy who does "nothing special" with the cards but ends up doing amazing things? Do you want to be thought of as a card sharp or a magician? I don't worry about doing what is "natural." I simply try to avoid doing anything overly suspicious and try to keep my cardwork relatively linear.
Assuming that you know the card's identity, is it possible to peek in the course of a shuffle/riffle , and get a break or see how many cards away it is from the top?
Yes... it's called "riffle stacking," and it isn't easy. Darwin Ortiz's books & videos are one place to start learning this sort of stuff. You might also want to look at Ortiz's annotated edition of Expert at the Card Table.