Google Image search is focused more on matching meaning than matching images. If you want to search for instances of an image (to watch for usage of your organization’s images or to find mentions of a chart or graph in a report or article, say), you’re better off using a reverse-image search tool like TinEye instead.
A use of reverse image search I don’t often remember is to see if you’re looking a legitimate profile in social media or a fake. Right-click the person’s image, copy the URL and search for other instances of that image. If it’s a fake profile, it’s likely that whoever set up the profile used an image that appears elsewhere on the web, often a stock photo.
Remember Google’s undocumented (i.e., not in Google Help) prefix searches. You can use intext: to look for words in the body of the page, intitle: for words in the title, inurl: for words that appear in the URL itself; and inanchor: for the words that appear in the anchor text (the text that’s highlighted in a hyperlink). Remember that you can’t have a space between the prefix and your search term — use intitle:asteroid to find web pages that have the word asteroid in the title, for example.
And I just learned about a new top-level domain – .graphics, so you can look for web pages specifically pertaining to computer and data graphics by searching for site:*.graphics.
When researching a topic, consider whether you want to search by process (how do I do this activity/thing?) or outcome (how can I get this result?). You’ll use different words and find different results based on which perspective you take.