When you find out, blog about it. But I imagine you have to be a recognized expert and thus invited. But then again, it probably wouldn't hurt to ask local groups if you can speak.
You can be a INETA Speaker by invitation only. And AFAIK, each INETA region has a different speaker bureau and different rules on membership. So I am not sure if you could really go around the world being an member of INETA speaker bureue. I would really recommend, that if you do go around, you let the local UG lead know and I am sure he/she will be more than willing to have you speak at their group.