For example, a main useful one would be Quora. Are they considered reliable. What if the answer has sources. Then can we it or do we look at the sources? How about if it is unsourced?
IMHO Quora is mostly unregulated junk. There are a few good posters there on space topics as long as they stay in their respective wheelhouses: former astronaut Clay Anderson; ISS instructor Robert Frost.
The kind of sources that lead to credible answers are space agency documentation and official websites (usually - NASA has been known to produce some howlers in their quest for understandability); products of reputable news organizations; aerospace company documentation and official websites; textbooks, memoirs, and histories.
Some Internet Guy - no.
Organic Marble's answer is great, but I want to add some supplementary ideas and I think this is going to end up too long for a comment.
There are a couple of good ways to think of sources:
How far removed is the source from the actual information? Primary sources come from the people involved (diaries, memoirs, published technical papers). Secondary sources build off those primary sources (press releases, news articles). Tertiary sources build off secondary sources, etc. Note that this doesn't actually speak to quality of information: I can fill my diary with lies and it'll still be a primary source about my experience. There's biases, there's mistruths, misunderstandings. All that tends to accumulate more and more as you get further from the source of information though.
Something perhaps even more worth noting is whether or not you can even tell how far removed the source is. Secondary sources, news articles in particular, like to cite each other or make vague citations of information that may not be available to the public--or maybe the information IS available and they just don't link to it. In contrast, something like a NASASpaceflight.com forum post shows its work and the original photo it's building off of. That does leave it to the reader(s) to then evaluate if that work is sensible or not (see my later big point), but at least it can be evaluated rather than just taken on the author/publication's authority.
How consistent is a source with information we're already confident in? It's easy for people to be fooled by only caring about where information "comes from;" for example, every couple years there's another press cycle where you can dig in and find actual press releases / papers from people affiliated with NASA or SpaceX that turn out to be utter trash (see e.g. anything from Sonny White or "Eagleworks"). There are posts on this very StackExchange that are full of unattributed, made-up numbers, yet they haven't been deleted. Fortunately, if we keep physics and our day-to-day experiences of reality in mind, we'll be led astray less often, though even debunkers have to apologize sometimes and sometimes it turns out the industry narrative is wrong (maybe reusing rockets can lead to cost savings!).
So with that said about quality of sources, no matter what source you use, be honest about it. If you want to use a source that you think is doubtful, like a Quora post, but still think it actually contributes something, point to the post, quote the relevant bit, and point out why you think it's still useful. One of my earliest answers here includes a quote from a usenet post from an HVAC newsgroup. The quote is complete enough that the reader can judge for themselves how seriously they want to take the source. +5 score is probably about right for that answer; not great, but not awful. Probably also the first time I got in a spat with another user here (sorry uhoh).
Of course "get good at rating the quality of and properly using sources" is hard advice to really follow, but it is a skill that can be cultivated. Listen to community feedback about your sources, edit your posts, and continue to improve your posts over time, and you'll thrive.