It's bound to come up in questions but where do we draw the line for ET, Aliens and UFOs?
I would say that as long as it is
Directly or closely related to the topic of space exploration
The we are OK. For example, my question, Has any country stated its official position on how it would respond to a discovery of intelligent extra terrestrial life?, would fall into this category. It is closely related to space exploration in that ETI would probably be discovered through space exploration.
We need to be careful, though, that we don't say things like this: My question is about manhole covers. Flying saucers are shaped like manhole covers. We might discover aliens through space exploration. Therefore, manhole covers are on topic here.
We could apply that logic to anything - peanut-butter and jelly sandwiches, desk chairs, dollar bills, what have you.
The difference, however, is that it's not closely related to space exploration. It's a fourth cousin, at best.
Therefore, we need to think a good deal about whether a question is closely related to the topic before and after asking it.
It is a 'fun' topic, but it should be handled with some respect. Even some of the greatest minds in the business like Carl Sagen have hypothesized about this topic in a rather rational manner. Strangely enough, the sheer thought about alien live drives a lot of planetary scientists, for instance, in the back of their minds, so it is in fact a fair topic to discuss.
ET, Aliens and UFOs = Out of scope
While the potential for intelligent (or not) life existing on other planets is significant, it remains a subject of pure speculation.
All due credit to believers, there is no scientifically credible support that any intelligent life is within several hundred light years of us. We have been broadcasting for nearly 100 years and, listing for several decades.
Given the current state of knowledge, there is no reasonable expectation that any person alive today on the planet earth, will or could have knowledge of or communication with extraterrestrial intelligence.
Non-intelligent life within in our solar system, and potential methods and locations for identifying = In scope
Given the current state of knowledge, there is reason to suspect that at the very least microbiological life does exist and can be found extra-terrestrially in our solar system.