How to know when he's ready?

When you see him squatting and grunting take him to the bathroom and put him on the potty. Be sure to take the diaper off. I simply took my boys to the bathroom at regular intervals. About 15 minutes is a good one to start with, especially if he doesn't potty the first try. If he fights sitting on the potty, at all, don't push the issue. Wait a little while. He will let you know by actions when he is ready. My mom was potty trained at 9 months because she literally would hold it in and scream until my grma put her on the potty. Of 5 kids in my family, the oldest to potty train was 18 months. We were all in cloth diapers.