by checking the sources cited in a news piece as well as the terminology. For example, if you read an article or see a news story on a political or economic topic, who do they quote? How much time to they give to presenting both sides? It's very common for a network news story to only quote Democrats when presenting a political article. Other times, they may include a token quote (usually a one-liner) from a Republican but that's almost always drowned out by the time given to Democrats. That's an example of bias, as is when the reporter frames his article from the Democrat's perspective without considering the other side. I see this on the news virtually every day.

Another manifestation of bias comes in terminology used to describe organizations. For example, if a reporter quotes the Cato Institute or the Heritage Foundation, he/she almost always will call these conservative organizations. Fine. Why don't they also label organizations like the Brookings Institute as liberal? Similarly, I've frequently come across the phrases "far right" or "radical right" when used to describe conservatives. How often do they ever label a liberal as "far left" or "radical left?" That too is an example of bias.

Yet another example is when you have a group of talking heads on a news program. It's very common that you'll have a supposedly independent moderator, a couple of Democrats, and a sole Republican. Once the discussion begins, you can quickly see how "independent" the moderator is when he joins in with the Democrats at jumping on the Republican. I guess they think a 3:1 advantage is necessary to debate a Republican. Perhaps they're right.

The point is simple - it isn't hard to spot a left bias in the news. It doesn't mean there's some conspiracy, it's just that a majority of the Press leans to the Left and that just comes across with their reporting.