the only way i know to do this globally without checking to see what words are extending into the margins is to use \sloppy, and you really don't want to do that. the resulting interword spacing is often terrible, and
it can change previously "good" paragraphs.
the next easiest method is to look into the log file for overfull hbox messages, determine what words are involved, and add those with appropriate break points into a \hyphenation{...} list in the preamble.
if there are true exceptions, that aren't handled by this method,
look to see whether they may be compounds with explicit hyphens -- those
won't be hyphenated automatically. you can define a command \hyph to
replace the explicit hyphen in a way that enables the automatic hyphenation
routine to take effect. see Force hyphenation for a word beginning with a digit for the definition and
rationale.
finally, if none of the above is applicable, insert "discretionary" hyphens
into the affected word with \-, as in "hy\-phen\-ate".
draftoption on the class and see the black marks on the margin showing the overfull. Usually you have to change a little bit the text around to solve the problem. – Sigur Jul 22 '15 at 16:55\setlength\overfullrule{5pt}it does the same thing. – daleif Jul 22 '15 at 18:36\overfullrule{<dimension>}is the width of a rule placed on the output at the right of the line (or block of lines) that exceed the right margin. the purpose of this rule is to make it immediately obvious what is too wide. if there is a large blank space before this rule, then the problem is most likely a box that is defined to be wider than necessary. – barbara beeton Jul 24 '15 at 04:39