On most spells before it tells you what is says it says say / chant / whisper / yell but do you really need to do that? well chanting is just like talking but faster, say is normal talking and whisper is talking quietly.
Personally I think that you can say it any way you want as long as you are passionate you could say the spell in sign language. Take me for an example I really love to sing so I sing my spells. I find that it works better for me than just saying it. So do whatever you want!
here are some tips
know how to pronounce your spell
try to remember it because spells work better with your eyes closed
have confidence that it is going to work
the phase of the moon will affect your outcome make sure you know what the moon phase is