My son will be 9 months old in about a week and he still isn't crawling. He rolls around on the floor but doesn't really show any interest in crawling. How do I get him to start?

Different baby develops differently. Some babies skips milestones. My little brother totally skipped crawling and started walking and running! It got our mum worried for a moment. My first born only started crawling at 11 months which is kind of late but doctor say it is fine as long as he is healthy and growing well. My second born started crawling at 7 months which is early. So give them some time, they will definitely catch up on it! You can introduce more tummy time and let him get the hang of it.