Go to the rules folder where you downloaded the VRT certified rules during your Snort install (by default on Windows this will be C:Snortrules). If you have not yet installed these rules please do so. If you have any trouble downloading the current VRT rules release package you can retrieve them fromhttp://polaris.umuc.edu/~sgantz/files/snortrules-2982.tar.gz on my UMUC Polaris server. In the compressed (zipped) package you are looking for the files that end in .rules extensions.
Pick one of the named rules files open it and choose a rule. If this is your first exposure to Snort rule syntax please note that the rules are the sometimes-cryptic looking items starting with the word alert. Copy the rule you pick into your response and describe what the rule means in your own words.