Maltego is very cool, but it’s also just one tool. You may try searching for OSINT (Open Source Intelligence) and review the documented techniques and tools that could help you discover the information you are after.
There are also groups/companies that develop commercial plugins designed to boost intelligence gathering capabilities – like SocialNet. Sometimes these tools can be challenging to use because they violate the Terms of Service of the target systems.
Outside of using specialty tools searching via the popular search engines is bound to help. A caveat is to learn search engine limitations that impede OSINT work. Paterva & FOCA Pro training courses talk about search engine limitations – here is an example:
Exalead reports 20,227,717 search results for "john smith":
But when trying to retrieve results after 2,000, you'll get: