It's a tragedy that the word "skeptic" is often conflated with "denialist" and all the strong emotions that go with it. Calling yourself a "holocaust skeptic", or a "global warming skeptic" can get you dirty looks and worse. But a skeptic is merely a person who holds judgement on new claims until evidence has been presented and checked, nothing more. But this is also like saying penicillin is merely a peptidoglycan antagonist or that iodine is just a cytoplasmic oxidizer. It's technically true, but it says nothing about the effect that they have.
Skeptics are used to clean and sanitize both science and everyday commerce, and the result is a system that runs better. When a skeptic approaches a new theory or claim, the objective is not to kill it, but to clean it. This can mean that initial work has to be thrown out and re-done, sometimes leading to a different conclusion, but this is normal in the everyday world as well.
In science, a good skeptic can eliminate many spoiling factors, including:
Skeptics can be seen as part of the QA (Quality Assurance) process, and it's unfortunate that the methods they have to use can generate a great deal of resentment, not just among the people doing work that comes under a skeptic's attention, but to the cheerleaders and impatient beneficiaries. It's important to have faith that when a skeptic tears apart a badly prepared report and sends everyone back to the drawing board, the final result will be better and more effective in the long run.
Skeptics are like antiseptics in a hospital operating room. They make sure the room, table and instruments are all sanitized, or else the patient might die of a post-op infection. When science gets politicized, as it has happened with anthropogenic global warming (AGW), it's like letting a germ warfare agent into the operating room. You'd need extra strong, heavy-duty antiseptics to make sure the patient doesn't get an infection, and in politicized sciences you need extra strong, heavy-duty skeptics to prevent the science from being killed and its corpse animated for political ends.
AGW is a magnet for politicians because it can be used to justify huge spending projects on one hand, and as a pretense for crippling the economy of nations on the other. Since the stakes are literally measured in hundreds of trillions of dollars over the next century, it will be necessary to employ the strongest, thickest-skinned skeptics to keep the science as contaminant-free as possible. The consequences wouldn't just be as bad as a dead patient, it'd be as bad as millions of dead patients if we spend all of our resources on the wrong measures and melt the ice-caps anyway. Our worst outcome is if the climate-change deniers are wrong, but we still wasted our efforts on the wrong remedies.
This means placing skeptics at the source of AGW research as well as in the public forum. A good QA agent isn't afraid to offend the chef when he sees a fly in the soup. He'll send it back to the kitchen before the customer has a chance to see the fly and reject the whole restaurant altogether. In the politicized global warming debate, however, this is very difficult to do. The skeptic will point out the fly in the soup and say, "that's a fly in the soup", while the global warming cheerleaders wave their pom-poms and say, "no, that's extra protein."
One of the flies in Al Gore's soup "An Inconvenient Truth", for example, is actually a mosquito. In his film he presents the case of Nairobi and an increase in malaria, which he claims is due to global warming bringing warmer temperatures--and with it mosquitoes--to a city that used to be "above the mosquito line". Alas, while other examples of AGW in the film may be defensible, this one is bunk. An inconvenient consequence, now, is that spectators are rejecting the movie, the book, and sometimes the whole message because they don't know what to believe. This could be a disaster if the core claim of AGW turns out to be true.
While I've chosen AGW as my main example, skepticism is something that you should practice every day for every claim, not just scientific or propaganda claims. It's a major critical thinking skill that will make you smarter in less than a day. The following are the basic steps, with some examples:
And always ask lots and lots of questions.