Where to Find the Advanced Search
You can find the advanced search in the Settings menu on Google's home page, or on any results page, under Settings/Advanced Search.
Any of These Words
On the Google Advanced search screen, you can take advantage of "any of these words" for similar concepts. In this example, if you're looking for information on the safety of hyperloop technology, you might want results with any of the words, safety, crash, or terrorism.
None of These Words
In this example, let's say you are looking for information about the Riverside Bridge, but you are getting results about the Riverside Bridge Club (the card game called Bridge). In order to remove results about the game, you can use "none of these words," and enter "games club." That will remove results that contain those words from your results.
Limit by Region
Let's say you did the search above and got results that were more relevant (about bridges instead of the card game bridge), but it still wasn't the bridge you were looking for (since many bridges around the world are called Riverside Bridge). In that case, you might want to limit by region. If you know that the place you are looking for is in the UK, you can select "region: United Kingdom." That will give you results from that region, very likely bringing you to the information you are looking for.
Limit by Language
Let's say that you are learning Spanish, and you don't normally search in that language. You can use the option "narrow your results by: language," to find articles in Spanish about your topic.
Here we find results about the artist Frida Kahlo, written in Spanish.
Limit by Site or Domain
Suppose you are looking for some opinion pieces about the "uncollege" movement. It can be interesting to compare results from different types of sites, such as from commercial sites versus educational sites.
You can do this with the feature, "narrow by site or domain." In this example we entered ".com" for results from commercial sites.
Here are the results. They may not be very different from results if you hadn't filtered to ".com" sites because often those sites come up high in the rankings anyway. So let's try switching it to ".edu" sites for comparison.
Here are results after filtering to just ".edu" sites. These might be interesting and surface some articles from different points of view than those you found in the initial search.
For some ideas on which domains to try, see A List of the Most Common Internet Domain Extensions, and Internet country domains list.
Where Terms Appear
Another useful feature on the Advanced Search page is "where terms appear." Sometimes the keywords you're looking for are on the page, but the page isn't primarily about that topic. If you search for your terms in the title of the page, you can get more specific results.
Links to a Page
Another useful feature in the Advanced Search is the ability to look for your terms appearing "in links to the page." This will help you find pages that link to a particular site.
Narrow by File Type
If you are searching for a certain type of document, you can use the "narrow by file type" feature. For example, let's say you want some trend reports about artificial intelligence. These are often published for free online as PDFs. Use the selection to narrow your search to PDFs, and you can often come up with useful results. There are several other file types in the menu, such as Microsoft Word, Powerpoint, Excel, Google Earth files, and more.