This is actually a FAQ, (La)TeX makes overfull lines. The simplest and best solution, as @Canagreek mentioned, is to load the microtype package. This will greatly reduce the number of overfull lines, and generally make paragraphs look much better (uniform greyness and fewer hyphenated words).
If you still get overfull lines, and are willing to accept quite ugly paragraphs, you can add the command \sloppy command. This sets the \tolerance mentioned in @Marco’s answer to 9999 (the largest possible finite value), but also changes a few other parameters. The opposite of \sloppy is \fussy (and is the default).
Also make sure you load the correct hyphenation dictionaries for your text, e.g., \usepackage[UKenglish]{babel}. Otherwise, TeX may have trouble find hyphenation points for words, or use the wrong hyphenation points.
methodcauses the "violation", output in your.logfile as "badness". Rewording your sentence would work. – Werner Nov 13 '11 at 20:04