There is no real "right" age. There's right for each child. There's are checklist you can find online (they all look a like, frankly) that outline readiness cues. In fact, both major diaper brand web sites have the list posted somewhere on their site. See if he's meeting those cues.
I think my DS was about 18 months old when he started showing interest in the toilet. We got him his own little potty and let him have his way with it. He'd drag it around, sit on it, pretend to use it and then rush to flush the toilet. He wasn't actually ready to ditch diapers though. LOL! When he was 27 months old, we started talking more about giving up diapers. He would use the toilet (potty seat placed on it) but he wouldn't use it consistently. At about 31 months old we toured the preschool he'd attend. He wanted to start THAT day. We told him first had to learn to use the potty. Within a week he was out of diapers. He was simply ready then.
at 12:04 PM on Feb. 28, 2011