Considered the father of modern public opinion polling, George Gallup created the Gallup organization renowned for its scientific polling.
Another reputable, scientific polling company is Rasmussen Reports.
How else could you improve the accuracy of polls? Some people think that if the sample had some skin in the game (a greater interest) in the results, they would choose their answers more carefully. To that end, the Iowa Electronic Markets creates a public opinion tracking poll by treating presidential elections like the stock market wherein individuals can purchase shares of candidates.
How did Nate Silver famously predict the outcome of the 2012 Presidential election so accurately? By looking at polls across America (and weighting the polls based on their historical accuracy). Check out his blog.
Interested in learning more about the history of public opinion polling? Check out this great resource from PBS!