In philosophical and historical terms we would locate its origins and usage within the context of The age of Enlightenment and Empiricism. Destutt de Tracy believed that his science of ideas would reveal to men the source of their prejudices and biases. He also believed in only trusting 'sense' impressions.
However the modern use of the word is largely attributed to Karl Marx and his philosophical disciples.(Marx's book German Ideology is a good example)
Present usage of the word tends to be rather broad and is used to characterise, ideas, ideals, beliefs, values, religions, political philosophies, moral justifications or simply a 'family of concepts', thus we are able to consider 'popular movements' such as Punk or Hip Hop as well as more formal religions and political movements as having an 'ideology'.
Ideologies may be seen as a 'family' of justifications that masks a specific set of interests. For the Marxist a whole range of smaller ideologies are essentially there to mask the larger systematic, ideological exploitation of the 'worker' by the elite 'ruling class'.
The Marxist thinker, Althusser, makes some very interesting observations about the features of ideology one of the most striking being that ideologies do not invite or tolerate criticism rather they tend to require obedience.
Guidelines for academic usage.
Because the term ideology is so large when using it in an academic sense I would suggest it is advisable to define what you mean by it. Do not be afraid to set either a context or boundaries for yourself or your reader. Just make sure they and you conform to and understand the reasons for the boundaries you set. For example you may wish to narrow your focus on religious ideology or on the specific ideology of a specific religion...in which case aspects of political or cultural ideology may be irrelevant to the focus of your argument or essay. Setting boundaries at the beginning of an essay in general prepares the reader for a bias and has the added value of directing the writer (should he/she feel the tendency to wander or waffle) back to the strait and narrow!
There are a good many books in the Library that cover ideology ... I would strongly suggest browsing a variety of books and discussing with friends this tricky topic ...I hope I have helped to opened the door to this very large and interesting subject, an understanding of which is very important to performance theory. There can be little or no deeper understanding for example of Shakespeare, Brecht , Stanislavski, Performance Art, Modern Dance, Popular Music, Opera, Classical Ballet, The Musical etc, etc without an understanding of ideological context.
Michael Moor