Your baby might start sitting as early as 4 months old or as late as 9 months. Don’t try to rush it. You should make sure he has some specific large motor skills such as he should be able to hold his neck up, have some balance, and have trunk muscles.
Once your baby can sit alone, you’ll need to make some adjustments to his room. By 6 months, his arms are very strong and he will be grabbing for everything. Check the crib’s surroundings and put anything dangerous out of reach. For example, you’ll want to remove mobiles charging points and mobiles above baby’s reach so Baby doesn’t get caught up in the mobile while pulling on them. Also, lower the crib’s mattress so he won’t be able to get out of the crib.