Here is an example of a link which activates a Google search: Tip of the day, on Wikipedia
It was built using this wikilink:
[[google:"Tip of the day"+site:en.wikipedia.org|Tip of the day, on Wikipedia]]
Sometimes it is useful to place a link to a Google search directly in a discussion. You can also use links to predefine an entire search session, and then use a tool like WP:LINKY to open the searches all at once into separate web browser tabs.