Traditionally it is recommended to speak in present tense, as if you have already gotten the result that you want. However, I don't think that's something that can mess up a spell if you don't follow that - I would advice you to follow your personal taste.
Words or want? You should want something when you cast. I don't think I've ever said the words very loud, and it's worked for me. Many say you should say them out loud, perhaps shout them, but I usually whisper them when I actually say them and I've been successful. The want will add extra fuel to the spell. You might want a date because you like someone, and that want will add to the spell. At the same time I know plenty of people who sell spell kits/candles/enchanted items to people and they work wonders, so do what feels right to you.