Is your baby right-handed or left-handed?
I could have told you from a few months old that my older son was destined to be a lefty. Now, through no intervention on my part, he’s quite ambidextrous, but definitely left-dominant.
Some experts will tell you that lateralization doesn’t happen until 4 or 5 years old, but I think (and I’m not an expert) that kids show signs much earlier.
What hand does he use to feed himself? Which hand does he use to throw a ball, stack blocks or turn the page of a book?
Around 9 months, babies can cross the midline, meaning that they can reach across their bodies with their right hand to pick up something on the left side, or vice versa. They won’t be able to distinguish right and left for a long time, but you might get an early hint from how they approach a staircase (dominant leg will lead), pick up their Cheerios or grab a Crayon.
You really don’t want to encourage one or the other. There’s not a benefit or detriment to a dominant side; it’s just nature. Let baby work with both to discover what he prefers.