There are many levels at which one reaches before they become a believer. I personally believe we are all skeptics to a certain level, but some people are more willing to listen to a story based on little-to-no evidence, and believe it on faith.

Some however, will scrutinize until it has been debunked, or a top level official has declared the subject as fact.

So, what would it take for you to believe in a certain conspiracy? Are you someone who believes the accounts of say, Jesse Marcel, Col. Phillip Corso, Werner von Braun & Ben Rich?

Are you more open minded to ideas from people such as say... Bob Lazar & Gary McKinnon? Or are you a hardcore skeptic, for whom it would take a Presidential address to make you believe?

Yeah, I mean you even have people arguing about what Dmitry Medvedev said recently, about the Men in Black. Some people aren't sure whether it was a joke or not, and because he was president of Russia, people have taken it as a sort of leak of information, when it could and mostly likely was just a joke.

how can a russian leader joke, that's just the russians. he could have been telling you or being smooth with you.

i bet they were laughing it up later with their buddies over some very expensive alcohol.

One just need understand human nature in order to believe that individuals and groups in power will do whatever they can to stay in power or that those who seek power will do whatever they can to gain it. All of the above will make alliances, temporary or longterm to achieve these goals.
As far as specific conspiracy theories, one need understand that plausible doesnt equal probable and circumstantial evidence is not a smoking gun. Also, that everything can be connected and finding some random connections does not equal a conspiracy theory. Take JFK conspiracies: It's very probable, based on evidence, that there is more to the story than a lone gunman assassination. But once you get into specifics, things become much more speculative and into the realm of plausible but unlikely (Federal Reserve, CIA, preemptive strike to alien disclosure, Illuminati, etc)

Perception is everything. First off when a person builds a reputation/character of truth and pins his name to it; transparency and forth coming on all information & Straight answers.
Then I begin to pay attention. Pictures are nice but as we have found out images can be altered.

Here is good example of one I would believe first and verify later: Ken Hamm

which would be a good read for everyone here ATS.

As soon as the US Government officially denies it, I believe it. If a casino were taking bets about whether the government was lying or telling the truth about any given issue, you could clean up by always betting on the lie.

Easy. Disclosure is only theory until proven right. Proof after the fact. Proof.