General Tips
Focus on the content and the logical format of a document. Let TeX
take care of the visual formatting
A main design goal behind TeX and LaTeX is to relieve an author of the
burden of having to be concerned with the visual appearance of a
document. Given the basic structural elements of a document,
TeX is very good at creating a professionally looking typeset output.
All TeX needs to know is the logical function of a
particular chunk of text, e.g., whether it is a title (indicated by
"\title{...}"), a
section heading ("\section{...}"), a list item (\item{...}),
a theorem (\begin{thm}...\end{thm}),
an inline math expression ($...$), a displayed math
expression (\[...\]), or ordinary text.
Given such information about the
logical structure of a document,
TeX will take care of all the rest, e.g., what fonts to use, how much
space to insert, where to insert linebreaks within text, whether to
center a header, or whether to indent a line. TeX is very good at this,
it (or rather its author, Don Knuth) knows more about typesetting
conventions than almost any author, and it has very sophisticated
algorithms to optimize such things as line and page breaks.
Below are some examples of visual formatting that you should
avoid.
[There are situations where some manual formatting may be appropriate,
in e.g., nonstandard (i.e., not "article/book type") documents such as
exams, announcements, posters, etc., bibliographies, etc. However, for
normal papers, books, and theses, such commands should be used very
sparingly, if at all.]

Manual coding of titles and headings.
\begin{center} \LARGE Introduction \end{center}, etc. Instead use
appropriate logical constructs: \section{...}, etc.

Explicit font and sizing commands.
\textbf, \Large, \small, etc.
(To "highlight" a term (e.g. in a definition)
use \emph{...} ("emphasis"), a logical highlighting instruction,
rather than an explicit font instruction.)

Forced line breaks or page breaks within ordinary text.
\linebreak, \break, \pagebreak, \\, etc.
(Occasionally, a \linebreak or \pagebreak may be appropriate to fix a
bad line or page break; but this should only be a last resort.)

Spacing commands.
\hspace, \vspace, \bigskip, etc. These are almost never appropriate.
If the proper logical structures (\begin{proof} .... \end{proof},
\section{...}, etc.) are used, the appropriate amount of vertical spacing
is automatically inserted.

Forced indentations.
\indent, \noindent (Unwanted indentations are often caused by blank
lines, which TeX interprets as paragraph breaks. To get rid of the
indentations, just delete or comment out the blank line.)

Forced displaystyle.
\displaystyle. (In displays with the displayed math construct \[ ... \]
displaystyle is the default, so no explicit \displaystyle is needed. In
inline math, if displaystyle is forced with an explicit \displaystyle
command, the result usually looks very poor. Either don't use
displaystyle, or code the expression as a display, enclosed by \[ ...
\]. )

Spacing commands in math mode.
Spacing in math mode can be adjusted/finetuned with commands like
\, \!, \ . However, in most cases such adjustments are unnecessary
and make for poorer looking output
since TeX automatically inserts the appropriate amount of spacing.
Refer to the Gratzer book for the (very few) situations where TeX
doesn't get the spacing quite right, and manual adjustments may be
made. In case of doubt, just leave the spacing up to TeX. Even if there
are occasional imperfections, not fiddling with the spacing at all is
far better (and takes a lot less work!) than overcorrecting by
inserting lots of manual spacing.
Bottomline: If you let TeX do its job, the result will almost
always look better than if you were to try to use manual formatting
commands to force a particular look. On top of that, you'll save
yourself quite a bit of time by not having to insert manual formatting
commands and fiddling with these until the look is right.
Respect the modes of TeX: Use ordinary (text) mode for text, math mode
for inline math material, and display math mode for displayed equations
The basic "modes" of TeX are text mode, inline math mode, and display
math mode. The default is text mode, intended for
ordinary (English) text; this is what TeX uses without any special
instructions. A pair of dollar signs indicates to TeX that the enclosed
chunck is a mathematical expression and is to be typeset in math mode.
Similarly, a backslashbracket pair, or an equation environment such as
\begin{align} ... \end{align}, tells TeX that the enclosed material is
a formula to be displayed.
There are significant differences in the typesetting of a given chunk of
text depending on the mode TeX is in (e.g., the spacing rules are
completely different in math mode than in text mode), and if an
inappropriate mode is used, the output can look very poor.
Thus, it is important to ensure that TeX is in the correct mode, e.g.,
by enclosing all (inline) math material in a pair of dollar signs, while
leaving nonmath material outside dollar sign pairs. This might seem
like an obvious rule, but it is commonly violated.
Here are some examples:

Don't italicize words by placing them inside $ ... $.
The letters do come out italicized, but the spacing looks awful since
it is optimized for mathmode and the letters will be typeset as if they
were mathematical variables, multiplied together.

Enclose variables and numbers embedded in regular text
within dollar signs. For example, in the phrase "Let F be a field",
"F" represents a variable and thus should be enclosed in dollar signs:
"Let $F$ be a field."
The same goes for numbers, though there the differences between text and
math mode are more subtle: Instead of "In dimension 3 we have ..."
use "In dimension $3$ we have ..."

Enclose text material inside displays in \text{...}.
\text{...} causes the expression enclosed in braces to be typeset
in text mode. This is useful in displayed formulas that
involve some textual material.
For example, in the expression "f(x)= \sin x and g(x)=\cos x ", the word
"and" is ordinary text and thus should be typeset in text mode:
"\[ f(x)=\sin x \quad \text{and}\quad g(x)=\cos x \]".

Leave punctuation signs outside (inline) mathematical expressions.
A surprisingly common mistake is to include punctuation signs within the
dollar signs delimiting a math formula. Punctuation signs are not part
of the formula (they belong to the surrounding text), and therefore
should not be enclosed within the dollar signs. For example, in the
phrase "let $f(x)= cx,$ where c is a constant", the comma is not part of
the math expression and therefore should be outside the dollar sign
pair: "let $f(x)= cx$, where c is a constant".

Use modespecific font commands.
Most font changing commands come in two versions, one for ordinary text
(e.g., \textbf{...}), and the other for mathematical material
(e.g. \mathbf{...}). Use the version appropriate for the
mode, e.g.: "A \textbf{field} is ..."; Let $\mathbf{v}$ be a vector...".
Go by the book (i.e., Gratzer's book). Don't try to improvise
You probably know enough TeX that you could get by (sort of) without
further consulting books and references, and it is tempting to do just
that. This, however, would be a mistake that will cost you in the long
run.
If you come across something you
have never encountered before (say, how to put an asterisk on a
summation symbol to create a "starred" sum, or how to typeset binomial
coefficients), do not try to find a "solution" on
your own, but instead check Gratzer's book to see if the situation is
covered there. Any fixes you might come up with on your own are
likely inferior to the "book solution", and while they may not
cause immediate problems when compiling the code, they will probably
result in poorly looking output. Moreover, by continuing to do things
your own way, you will acquire bad coding habits that are hard to shed
and which, aside from leading to inferior looking TeX output, will
end up costing you time from using inefficient and wasteful coding
techniques.
Note on other Latex books.
By "the book" I mean Gratzer's "Math into Latex". This is the
authoritative reference on mathematical Latex.
The majority of Latex books (and online materials) don't focus on
mathematical typesetting, and while they may be useful for
nonmathematical Latex, many
offer bad, or outdated, advice on mathematical Latex.
As an example, almost all Latex guides recommend the "eqnarray"
environment for multiline equations, which has been rendered obsolete by
the "align" environment provided by the amsmath package. The "align"
environment produces better looking output, is more robust, easier to
use, and much more flexible. Gratzer's book is the only one that fully
covers this and similar environments.
Don't blindly copy other people's TeX code
Another very common mistake is to copy somebody else's TeX code.
Not everybody is an expert in TeX and produces code that is worth
imitating. In fact, the vast majority of papers that I have come across
are deficient in some respects, and would make poor examples.
If you want to write a paper in LaTeX, start from scratch, or use one of
the models in Gratzer's book as a template, rather that using
someone else's paper.
Back to the LaTeX Tips Page
Last modified: Tue 23 Aug 2011 05:49:44 PM CDT
A.J. Hildebrand