Orac has a nice discussion on the scientific consensus. An interesting question he poses is, at what point do you stop being scientific and start being a crank?

Scientific consensus is usually a good starting place to evaluate a claim. Martin Rundkvist makes the claim that, "A real skeptic always sides with scientific consensus." I agree with this point for the most part, and with Orac for thinking that this statement isn't an axiom. Scientific consensus is a very powerful thing, but like Orac says, there are varying degrees of its power. Certain consensuses, like evolution, are incredibly strong, while others aren't as immutable. Orac argues that straying from scientific consensus on certain issues is okay as long as the scientific consensus is weak, your reasoning sound, and as long as you use a skeptical frame of mind.

"It's more about tactics and how evidence is used to support an argument. Scientific skepticism looks at the totality of evidence and evaluates each piece of it for its quality. Cranks are very selective about the data they choose to present, often vastly overselling its quality and vastly exaggerating flaws in current theory, in turn vastly overestimating their own knowledge of a subject and underestimating that of experts. This is perhaps the key characteristic of cranks and the biggest difference between a crank and a true skeptic."

I agree, as long as you use caution when straying from the scientific consensus, and understand why the consensus is the way it is. Denialists and cranks often fall prey to logical fallacies, cherry picking data, and confirming their biases. Scientists know that this is a problem in human nature and that is why they use the scientific method in the first place. Of course scientists and skeptics have biases! This is why the scientific method is used, to protect from biases. Use of this tool is what separates us from pseudoscience and bunk.

Another question that comes up often is what if science has not weighed in on a claim yet, or it is completely ambiguous? The best tools to use then are humility and Occam's razor. Just because science doesn't know now, doesn't mean it won't know in the future. And it's unlikely that a extraordinary claim is true if there isn't an appropriate amount of evidence to accommodate it.

Via Respectful Insolence