Usually, the shadow Leader of the House asks a standard question about the business for the next week and the Leader replies, and sometimes indicates the business for the following week too. The shadow Leader asks a supplementary question and the Leader replies.
You then have an opportunity to ask a question about the business that has just been announced, or to raise a matter of concern. For example, you might ask “when the Government will find time for a debate on [subject of interest].” Such requests are unlikely to lead to actual debates, but are a way of raising awareness of the issue.
Occasionally, if an oral statement has been made first, the business is announced in the form of a statement, rather than a response to a question from the shadow Leader. This doesn't affect your chance to ask questions.
You can watch a video of a question being asked at Business questions: