You should always start with a mindful breathing meditation and then move into your mindfulness meditation. Starting with a breathing meditation will help you reap more of the benefits of the mindfulness meditation. Ideally, you should do the breathing meditation for 10-20 minutes and the mindfulness meditation for at least 20 minutes.
Until you feel it. Your body will respond, and mine response is crying. I realize I just needed to cry. Meditation isn't to make something but to feel yourself.