Use the \frenchspacing command; that makes the sentence spacing single spaced. You can revert it later on in the document via \nonfrenchspacing.
Personally I don't care either way about the spacing after a full stop. I tend not to notice it when I am reading anyway. I do, however, find that with paper drafts I'm editing, it is easier to visually locate the start/end of a sentence with the extra bit of padding.
Line-breaking
The classic paper about TeX, what (IIRC) DEK once called the main research output produced by the TeX project, is the paper:
[Reprinted in Digital Typography (1999), with some updates to notation etc. If you get an old printing of the book make sure to read the errata; there were unfortunately some significant typos.]
IMO even if you never use TeX or LaTeX, you ought to read this paper. It's a tour de force. In 66 pages, it introduces the line-breaking problem, formulates it mathematically, defines desirability criteria (badness, etc.), compares approaches, shows the power of this model (lots of sophisticated examples), then goes into the TeX algorithm with all its “bells and whistles”, before concluding with an inspiring history.
At heart, this paper is basically about TeX's elegant and powerful boxes-and-glue (or box-glue-penalty) model. By specifying an appropriate sequence of boxes, glue and penalties (to the same algorithm), we can elegantly solve many typesetting problems: not just for typical text (fully justified paragraphs) but things like centered text, hanging indentation, ragged-right text, typesetting program source code, book indices, quotations and author lines and blocks that should look different at different widths, paragraphs in various “shapes”, etc. After showing off these solutions, there is some theory developed (a kind of "algebra") that helps you come up with similar constructions yourself.
Many of these problems are also given in The TeXbook as double dangerous-bend exercises and in Appendix D: Dirty Tricks, but in the paper it's more expository. And most of these problems arose from real life, out of practical needs:
We wish to thank Barbara Beeton of the American Mathematical Society for numerous discussions about ‘real world’ applications;
An abridged version of this paper also exists:
- “Choosing better line breaks” (1982) by Michael F. Plass and Donald E. Knuth, in Document Preparation Systems, Nievergelt et al., eds. (Amsterdam: North-Holland, 1982), 221–242.
This paper, harder to find, has a lot of overlap with the previous one, except for some new terminology introduced (it uses boxes, glue and “kerfs” instead).
Best Answer
The default style of section headings are often present in LaTeX documents and rarely found in documents produced by systems outside of the TeX family.
Wider margins and a sane number of characters per line are features of most TeX'ed documents and many documents with these features have been TeX'ed.
Those first two can be overridden by a TeX user. The following two, much less so.
Proper ligatures (e.g. the way that the crossbars on "f"s will touch some following letters) are symptomatic of TeX.
My number one sign is relatively few hyphenations and much better looking line justification. You can make a TeX document have a line with bad justification, but it takes effort or bad luck. I've yet to be able to make a word processor have good justification.