Let’s think about the same question: “Discuss the influence of celebrity culture on mainstream culture” and consider the introduction (this is a fictional example, so don’t go looking for the sources I quote... I made them up!):

• Start with a catchy sentence, interesting quote, or relevant anecdote
  
  “75% of Americans under 35 years of age wish they looked more like their favourite celebrities; .01% of the American population are celebrities” (Mills, 2007). Celebrities have a significant influence over the lives of mainstream (non-celebrity) people.
   
• Define any major terms
  
  “A celebrity can be defined as... Mainstream culture is...”
   
• Set a clear direction for the essay
  
  “This essay will consider how the issues of body image and drug use by celebrities influence non celebrity culture...”
   
• Start with more general statements and end with a strong statement on your main point (thesis statement)
  
  “The influence of celebrities is significant and negative. Celebrity culture has a destructive influence on non celebrity culture.”