Use this tag if you are trying to identify a LEGO element or set that you possess or have seen somewhere.
Questions should include as much detail as possible.
The best question includes one or several pictures of the element or set that you want to identify. In case of elements, a picture with only the part is necessary.
If the element or set is yours, a brief description of it can help too, and possibly the circumstances surrounding it (such as a time period). Usually, a picture should be enough, but more detail can't hurt - for example many elements have an id number (Design ID) printed on them than can help to identify them.
If you don't have the element yourself, try to provide a picture of it; chances are you're wondering about the element because you've seen it, so let us see it too. Even a picture with the element being part of a structure is better than no picture. In addition of the picture, try to add as much detail as possible on the element or set you want to identify, such as where and when you've encountered it.
If the question is too vague, then it will probably be closed. If this happens to your question, please add more detail and flag it for re-opening.
This tag is not appropriate for asking for recommendations. If you're asking for a suggestion on which element to use, this isn't the right tag. Also, there should be exactly one correct answer - when someone does suggest the correct answer, please accept it, so that everyone else knows that there is no point making any other suggestions.