There is no 'proper' way because everyone is different. If you let your emotions guide you then you will find the proper way for you. As you make an affirmation statement take notice of how it makes you feel. If there is any resistance then simply reword it until it feels good. That being said..

I AM .. is one of the best phrases to use when trying to rewrite your subconscious. I AM is telling your mind that something is right now.