You can use speech marks to search for phrases e.g. "machine tool measurement" will find these words in this exact order and spelling, rather than finding the words individually (so you won't get information on machines, tools or measurement in general).
Use the Boolean operators AND and OR to modify your search. Make sure you put these terms in capital letters so that the software recognises them as Boolean operators - most search engines are programmed to ignore common words like these (and also things like the, of, in, etc.) so if they're not in capitals, they won't be used in the search.
AND narrows down the results by making sure the terms connected with it are guaranteed to be in the results e.g.:
"product design" AND "3D printing"
Using OR broadens the search out, by looking for terms that mean the same or similar things. Don't forget to use brackets to join any terms with OR e.g.:
("3D printing" OR "additive manufacturing") AND "product design"
Putting an asterisk at the end of a word will search for various different endings e.g. manufactur* will simultaneously search for manufacture, manufacturer, and manufacturing. However, do be aware that other words you don't want may be included, so be careful where you put the asterisk!
The below video gives a worked example of how to pick out keywords and synonyms from your research question. Remember, just typing your question into the search box won't bring back useful results: you need to think about what words researchers looking into your topic will have used.
Before you start searching, you need to identify the key terms in your topic, but sometimes just searching for those words isn't enough. You need to think around the subject, and sometimes use a thesaurus, to come up with all the different words that might be used to talk about the same thing.
For example, if you are researching 3D printing, you may also want to search for alternate terms for the same or similar processes, such as additive manufacturing.