A lot of the content you'll find online will be organized into a type of database. This means you can search them using the same tricks and techniques you use to search library databases.
This page will give pointers on phrase searching and Boolean Operators. Ask a Librarian to get more help with search strategies.
Some databases and search engines don't support Boolean Operators or wildcard characters. Many of them will state that near the search box, but you should be able to find more information about advanced search techniques in a website's Help or FAQ pages.