Some questions to ask yourself when looking at polls and polling data:
Who is the sponsoring agency?
Often the organization or agency sponsoring and/or conducting the poll has a particular bias and/or agenda.
What is the purpose of the poll?
This cannot always be easily ascertained, but often if you will take the time to look at the mission statement of the sponsoring agency the purpose will become self-evident.
What other questions were asked and in what order?
Often the purpose of the poll can be more clearly defined by looking at the other questions that were asked. The order can also be important. Are there "leading questions"?
Who was polled?
This is extremely important! For example, was this a poll of adults' perceptions of teenagers, or a poll of teenagers' perceptions of teenagers?
When was the poll done?
The timing of a poll is also important. For example, if you were asking U.S. citizens for their perspective of the Middle East before and after the the terrorist act of 9/11, responses would be dramatically different.
How were the interviews conducted?
How the polls were conducted can also be important. For example, were these polls conducted in "American Idol" fashion? These polls are conducted by surveying only those who happened to be watching the show that evening - not exactly representative of the entire U.S. population.
How large was the sample?
A good figure to keep in mind for a national sample is 1,000. Anything less is suspect. However, a smaller sample may be appropriate if it is only trying to measure a smaller population (e.g., Penn State teaching assistants).