You can specify global options or class options to the
\documentclass command by enclosing them in square brackets.  To
specify more than one option, separate them with a comma.
\documentclass[option1,option2,...]{class}
LaTeX automatically passes options specified for
\documentclass on to any other loaded classes that can handle
them.
Here is the list of the standard class options.
All of the standard classes except slides accept the following
options for selecting the typeface size; the default is 10pt:
10pt 11pt 12pt
All of the standard classes accept these options for selecting the paper size (dimensions are listed height by width):
a4paper210 by 297mm (about 8.25 by 11.75 inches)
a5paper148 by 210mm (about 5.8 by 8.3 inches)
b5paper176 by 250mm (about 6.9 by 9.8 inches)
executivepaper7.25 by 10.5 inches
legalpaper8.5 by 14 inches
letterpaper8.5 by 11 inches (the default)
When using one of the engines pdfLaTeX, LuaLaTeX, or XeLaTeX
(see TeX engines), options other than letterpaper set
the print area but you must also set the physical paper size. Usually,
the geometry package is the best way to do that; it
provides flexible ways of setting the print area and physical page size.
Otherwise, setting the paper size is engine-dependent.  For example,
with pdfLaTeX, you could include \pdfpagewidth=\paperwidth and
\pdfpageheight=\paperheight in the preamble.
Miscellaneous other options:
draft ¶finalMark (draft) or do not mark (final) overfull boxes with a
black box in the margin; default is final.
fleqn ¶Put displayed formulas flush left; default is centered.
landscape ¶Selects landscape format; default is portrait.
leqno ¶Put equation numbers on the left side of equations; default is the right side.
openbib ¶Use “open” bibliography format.
titlepage ¶notitlepageSpecifies whether there is a separate page for the title information and
for the abstract also, if there is one.  The default for the
report class is titlepage, for the other classes it is
notitlepage.
The following options are not available with the slides class.
onecolumntwocolumnTypeset in one or two columns; default is onecolumn.
oneside ¶twosideSelects one- or two-sided layout; default is oneside, except
that in the book class the default is twoside.
For one-sided printing, the text is centered on the page.  For two-sided
printing, the \evensidemargin (\oddsidemargin) parameter
determines the distance on even (odd) numbered pages between the left
side of the page and the text’s left margin, with \oddsidemargin
being 40% of the difference between \paperwidth and
\textwidth, and \evensidemargin is the remainder.
openright ¶openanySpecifies whether a chapter (or appendix, etc.) should start on a
right-hand page, by inserting a blank page if necessary. The default
is openright for book, and openany for
report.
The slides class offers the option clock for printing
the time at the bottom of each note.