If no words are coming - accept it. Sometimes, it's when you're with your best friend, or your mum, or the love of your life, and words aren't always necessary. Sometimes, that comfortable silence is priceless.
And if no words are coming, it's often because God wants you to slow down, to be quiet for a few minutes, and to listen to the thoughts whirring around your own head.
You'll suddenly realize you're obsessing over the latest incident at work, or the conversation you had with a relative, or whatever else it is God wants to bring to your attention.
Pay attention to your own thoughts and feelings, if no words are coming. See what pops up into your head, and then try talking to God about that stuff. This is often when some of the most amazing insights can occur.