In the "Welcome" meta-post, but also in the Help question "What topics can I ask about here?", https://economics.stackexchange.com/help/on-topic, as we have done already with the rest of the site-specific guidance.
I would also suggest to put our full site-specific guidance in another Help question, https://economics.stackexchange.com/help/dont-ask which appears first in the Help list under the title "What types of questions should I avoid asking?"
In my opinion it is totally unproductive that these two Help questions exist separately, but since this is SE-wide, I guess, and can't be changed, let's fill each with the same site-specific information.
A note: @Foobar offered a specific suggested text in an answer to his own proposal. Per previous discussions, the suggested text appears wordy, but the problem of homework/self study questions is so twisted that I believe demands a bit more explanation and guidance.
Finally: regarding "numerical content", let's be careful with questions that relate to simulations and/or Econometrics. These questions may present a case with specific data and specific numerical results / troubles, but in order to address them one has to go down to structure, so I think they should get a pass. For example somebody may not understand why a specific data set is giving him the estimation results it does, and pastes in his question all the relevant information: the answer will usually lie in wrong model specification or wrong software use, rather than arithmetic operations, and so it will be generally useful. Perhaps we should add something to @Foobar's suggested text on the matter.