Yes, it's perfectly OK to ask:

> What have you tried?

or:

> Please show your code.

or even:

> Please explain what you mean by "not working".

However, you should always be polite - remember the rule "be nice". We're trying to "make the Internet a better place" here.

If you need to add any (or all) of these comments that's the mark of a bad question. Leaving these comments is the first step on getting a good question that people can answer.

If there's no effort to improve the post then it's the mark of a question that can be closed.