On Physics Stack Exchange, people asking questions are expected to demonstrate that they've put a certain amount of effort into answering the question themselves. What exactly counts as sufficient effort?
What research do I need to do before asking a question?
Here's the general rule:
In particular, you should probably do all of the following before asking here:
If you find the answer to your question while doing all this research, great! You can, if you want, post your question here (if it's not already on the site) along with your own answer describing what you found.
OK, I didn't find the answer. Now what?
If your prior research didn't give the answer you were looking for, tell us what you checked. Don't explicitly list each one of the steps above to say that you followed it, but do mention anything you found that is close to the topic of your question, and point out why it didn't give you the answer you wanted. If someone reads your question and immediately finds a standard resource (Google search, Wikipedia, HyperPhysics, another SE question) that seems to answer it, it's going to look like you didn't do your research, unless you explain why that resource doesn't actually contain the information you're looking for.
What if I think I know what the answer is?
If you have a guess or hypothesis about the answer to your question (one that is grounded in solid physics), that's fine, but you should go out and check that hypothesis yourself. Maybe it'll be correct, in which case you can post the question here with your hypothesis (and the evidence that shows it's correct) as an answer. If you think it's incorrect, on the other hand, mention it in the question and say why you think it's wrong. A question that just ends on "My hypothesis is XXXX" comes across as lazy, but if you instead write "My hypothesis is XXXX, but that doesn't seem correct because Wikipedia says YYYYY," and so on, that shows research effort and makes a better question.
What happens if I don't follow these guidelines?
People trying to answer your question will follow the steps in the first section: they'll search Google, check on Wikipedia, on Hyperphysics, in textbooks, and do some simple calculations if it's that type of question. If, by doing so, they find the answer to your question, they're likely to downvote your question for not showing research effort. You may also get comments pointing you to the answer on Wikipedia or a top search result.
Sure, people shouldn't just blurt out whatever question pops into their minds without thinking about it and making at least some attempt to find the answer. The real question is how much is enough? What is a reasonable level of research? How do we measure that or even decide how much research was actually done? Should the bar be lower for a more beginner question?
I agree with the sentiment here, but I think our implementation sometimes goes too far. My answer here was brought about by this question. John Rennie wanted to close the question. His comment got 4 upvotes, and 3 close votes have accumulated so far. On the other hand, my comment saying it was a good question got 3 upvotes and the question itself got 9 upvotes, no downvotes, and three answers.
I think the real problem is that this is a rather "low level" physics question, and people are really responding to that. That's short sighted and will eventually leave only experts here with nothing to say to each other because nobody has anything to ask. With enough research, any question could be answered without asking here. This site is trying to be a repository of good questions with good answers. This can't happen if we refuse to answer anything that isn't answerable by other means. Even if the answer is out there elsewhere, for some questions we want this site to be where people go to do the reasearch and find the answer.
This site shouldn't be only about high-falutin physics. We aren't here for stupid questions either, but there is a important distinction between stupid and ignorant. The question I linked to above was ignorant but not stupid. It was well asked and actually about a clever observation for someone that doesn't already know the answer. That makes it a good question. Just because the answer doesn't require invoking relativity or quantum mechanics, doesn't make it a bad question or not useful to include in the repository.
Lighten up a little.
Added in Response to Comment:
David Z points out that this answer doesn't really answer the original question. That's strictly speaking correct. This was somewhat of a comment, but too long to be a comment. But, another point was that this is impossible to measure in a reasonable way and therefore will always be very subjective. To put it more directly, my points relative to the original question are:
So here is what I suggest someone should do before asking:
In short, there is a bare minimum amount of research anyone should do, but the appropriate level depends a lot on how advanced you are in the topic. The most important points are 1-3. After that it's mostly to ask a good question for your level that is self-consistant with that level, and to write the question properly.
It's OK to be ignorant, but never OK to be stupid. There is also never any excuse for sloppiness. Taking some care includes breaking thoughts into sentences, capitalizing the first letter of sentences, capitalizing the word "I", and never ever ever using text-speak.
Keep in mind that you are asking a bunch of people to volunteer their time to answer your question. If you keep that and rule #1 in mind, and show the appropriate respect by doing the simple things that have nothing to do with level of physics knowledge, you'll most likely do fine. Go ahead and ask.