Your best bet would be doing a reality check, like looking at your hands and spotting an extra finger, or look at a clock that is moving about/showing ridiculous numbers. Do that after you say that to yourself, then you should really believe you're dreaming. Then you should repeat that you're dreaming every few seconds, since you can lose lucidity so fast.

Don't hesitate to PM me or anyone with a green name (my name is blue-ish green, don't get them confused) with questions/concerns. See you around!