Wikipedia should not be used as one of your sources. However, there is nothing wrong with using Wikipedia as a starting point for research. Wikipedia can give you a good overview of a topic and reading the references at the end of the article can get you started on finding reliable, scholarly sources for your own research.
Most importantly, using Wikipedia, or another encyclopedia type source can help you define good search terms.
Should I use Google?
There is a lot of information available on the internet via a Google search. Not all of it is valid. The key is to find credible sources written by authorities on the topic.
In general, college and university websites which end with .edu can be trusted. Websites that end with .gov are associated with the government and can also be trusted. Websites that end with .mil are associated with the military and provide good insights into both history and policy.
Websites that end with .com, .org and .net are not as reliable. They are sometimes sponsored by commercial ventures or organizations who, in some way, profit from promoting a particular point of view. In other words, they are biased.
To limit your search to only a certain type of website use a site limiter (site:edu, or site:mil)
A sample search might be: site:edu ancient greece
More Google Tips:
|site:||search only within a specific site||site:www.harvard.edu|
|filetype:||find a type of file; PDF, DOC, TXT||filetype:PDF|
|define:||find definitions for a word||define:fugacious|
|intitle:||find words in the title of the webpage||intitle:nepal|
|..||get ranges of numbers, dates, or prices||earthquakes 1950..1999|
|word * word||find other combinations of words between words||global * warming|
|- word||search for one word, but not in combination with another||clinton -hilary|
|"word"||find exact words - no synonyms or plurals||"election" "fraud"|
|"set of words"||search for exact set of words, quotes or phrases||"I am not a crook"|
Try Google Scholar!
A subset of Google, Google Scholar only indexes article of scholarly worth.
There is a drawback - many of the articles are not available in full text. But, many of the articles I find on Google Scholar are available on JSTOR where we do have full access. So, in a way, you can use Google Scholar as a search engine for some JSTOR articles.
Additionally, using Google Scholar as a starting point can help you determine the best search terms for your project.