Here is a short extract from an article from Merseyside Skeptics

What is skepticism?
Skepticism is a method for discerning what is likely true from what is not.  When presented with a claim, a skeptic reserves his or her right to reject that claim until such time as the claimant produces sufficient evidence to back up that claim.  If the skeptic finds the evidence is compelling, then we will provisionally accept the claim as true; provisionally because we may see more evidence tomorrow that proves the claim to be false.
The quality and quantity of evidence required will vary from claim-to-claim and skeptic-to-skeptic.  If you tell me that you have a pet dog, well, I’ll probably accept that claim just on your word.  You’re not likely to get anything out of making up stories about owning a dog and I know that dogs are kept as pets by many people.  If you tell me that you have a pet dragon, on the other hand, I’m probably going to want to at least see the dragon before I believe you.
What isn’t skepticism?
Skeptics are not a collection of doubters and grumpy nay-sayers, gathering to reject, out-of-hand, any ideas which do not gel with our pre-existing beliefs.  Rather, we adhere to principles of scientific skepticism, a position which seeks to establish the veracity of claims through a logical and impartial evaluation of the available evidence.
We believe this to be the most reliable method to distinguish truth from fiction and uniformly apply these principles to any and all ideas – new or old, established or controversial.