I want to ask for a critique of my work? Can I do that here?
Are you coming to Writers with a specific question about a specific text you have written? Great. Writers is a community of professional and aspiring writers, editors, agents, and others in the business of writing, and we would love to help you.
In order for us to be able to successfully answer your question, it will need to fit within a few criteria.
What if my question doesn't meet these guidelines?
First, see if you can edit your question to make it meet these guidelines. Writing a good question is a process that can include re-writing. If at the end of the day your question is off the mark slightly on one of the criteria, you may consider asking it anyways. The community can help you tighten it up (or may determine that it is still on topic). If your question does not meet many of the criteria, it is likely to be closed if you ask it.
What if I don't have a specific question about my writing?
Give us guidelines for what you want your writing to do. Are you looking to create suspense? Do you want to provide an accessible explanation of a software product? Are you looking to submit to a peer-reviewed journal and want to know if your writing has a scholarly tone? Asking for a critique without telling us your goals isn't helpful, and we will follow up with asking for an edit and likely closing the question if you don't edit.
(Please note that, while the site doesn't support general, free-form critiques, you can bypass the main site and general critiques on our chatroom. Many of our users have gotten great general feedback there.)
What if I see another question asking for a critique that doesn't meet the criteria?
See if you can edit the question to meet the criteria without substantially changing the author's intent. If that is not possible and you have close permissions, vote to close. If you believe the question is a getting-to-know-you/poll type of question which is likely to garner lots of cheap reputation for all involved, please flag it for moderator attention.
Regarding posting excerpts from your work here:
An excerpt posted here could conceivable be looked at by a publisher as the basis of a later, published novel or story (or part of it). Does that mean that your novel must be published as Creative Commons or at the very least a derivative work of a CC work? Here's the Stack Exchange legal team's reply to this question:
Users can flag questions with excerpts and the like for moderator attention. Moderators can delete a question (which will limit its visibility significantly) and edit out proprietary/personal information. Intrepid users are also free to file a DMCA take-down request with Stack Exchange if need be.
(See the bottom of each Stack Exchange page for a link to the CC license and its terms.)
As always, ask a lawyer, but if you're concerned about this, use a link and don't publish the text here!
As of November 2014. See the explanation there for how to ask on-topic questions about your own writing. Bottom line: Ask the core question (about style or dialogue or plotting or whatever) instead of asking about your writing excerpt.