A general debate in Government time begins with a minister moving the motion. When the minister has finished, the Speaker will propose the question “That the House has considered…(subject)”. At that point, the debate begins.
The Speaker will usually call a frontbencher from the official Opposition, a backbencher from the Government side, and a frontbencher from the third largest party to make speeches next. The Speaker will then seek to call MPs from each side of the House in turn. You can seek to make a speech. There’s no fixed time limit for speeches, but the Speaker may set one if lots of MPs want to speak.
During the last half hour or so, the Speaker will usually call a second frontbencher from the official Opposition, followed by the minister to respond to the debate.
If the debate finishes before its scheduled end time, because everyone who wanted to speak has done so or because someone has successfully moved the closure, the House decides whether to agree the motion. There may be a vote. As the motion isn’t calling for action or expressing an opinion, the principal purpose of having a vote would be to show concern about the topic or how it’s being dealt with.
If the general debate is still underway at its scheduled end time, the motion before the House lapses, and the debate ends without the House taking any decision on the motion.