Beautiful LaTeX output is no accident — it comes from a few principles (consistency, trusting the defaults) and a handful of small spacing rules that separate amateur from professional typesetting. This page collects them.
Principles
Three habits matter. Consistency — keep headings, spacing, and fonts uniform across the document and let the class enforce it (write structure, not appearance, in the body). Trust the defaults — LaTeX’s spacing and line-breaking are excellent, and manual \vspace or \\ tweaks tend to cause drift (see “Line and page breaks”). Restraint — few fonts and sizes; let whitespace and hierarchy do the work. The less you fight LaTeX, the better it looks.
Punctuation & spacing
Western text has fine conventions. Sentence spacing — by default LaTeX puts a slightly wider space after a sentence-ending period (US style); declaring \frenchspacing makes all of them equal to the inter-word space (common outside the US). Abbreviations — a period after a lowercase letter is read as sentence-end, so use a control space e.g.\ or a tie Fig.~1; after a capital, write NASA\@. so the period counts as sentence-ending. The thin space \, goes in digit groups and before units (5\,kg), and the tie ~ keeps things from breaking across a line.
\frenchspacing % 文末ピリオド後を均等な空きに / equalize after sentence periods
Fig.~1 % ~ = 改行しない空白（タイ）/ non-breaking tie
5\,kg % \, = 細いスペース / thin space
e.g.\ this % 略語のあとは \ で語間スペース / control space after abbrev.
NASA\@. Next. % 大文字後の文末は \@ / mark sentence end after a capitalFull-width vs half-width — Japanese punctuation
In Japanese, digits and Latin letters are half-width, while Japanese punctuation (。、（）) is full-width. Getting the widths wrong looks off. The gap between Japanese and Western text is inserted automatically, so do not type manual spaces around Latin words. See “Japanese typesetting details” for more.