Say it out loud if you want but the most important thing is belief, you have to believe in 100 % that you will recgonise that you are dreaming or what ever your affirmation may be. Maybe it sounds harder when I say you have to believe in 100 %, but what I mean is that it's not that hard as you might think it's actually easy to succed a MILD It's hard to believe in the beggining, but when you have your first lucid dream it will become easier. and it doesn't matter if you say it out loud or in your head, but maybe it's better to say it in your head because you want to go to sleep x) but try to say it quietly until you fall asleep I have never done that maybe it's better, would be fun to know Good Luck!