What is happening socially, culturally, politically or economically that would warrant such a portrayal? What does this portrayal reveal about contemporary society. You may want to ask how such a portrayal reinforces or contests particular ideologies?

Start with a specific issue you are interested in critiquing in advertising. Below are potential starting points for your analysis

Start by asking critical questions as to why advertising is portraying something in a particular way.
What is happening socially, culturally, politically or economically that would warrant such a portrayal? What does this portrayal reveal about contemporary society. You may want to ask how such a portrayal reinforces or contests particular ideologies?

You could look at the ways a particular advertising campaign, or issue, or advertising medium, promotes the ideology of consumer culture.

For ideas on topics look up the Journal of Consumer Culture. There are lots of great scholarly articles in there.