I honestly had no idea my daughter was going to start talking until she did. She'd babbled for months, nothing that sounded at all intelligible. There were a few times right before she said her first word when I thought she repeated part of a song I was singing to her. I'd always sing while I changed her nappy and a few times it sounded like she said one of the words back to me. I kinda just thought it was coincidental though. Actually what really got her to start talking was finding something she was really interested in. We went to visit family who had a cat. She'd never really been around a cat much before. She was fascinated with it. She'd laugh hysterically when ever it came near her. Then suddenly the second day we were there, she just pointed and was like 'cat!'. It was that simple. I just think she'd never really found something fascinating enough to want to talk to us about it until them. Since then the words she always picked up easily were just things she was really interested in or curious about. So I would just focus maybe on words for things he likes doing or toys he likes playing with or his favourite foods and see if you hit on something. My husband didn't speak until he was 2.5 (he caught up fine after that and the speech delay didn't cause any lasting issues) and his first word was 'tractor' because he was obsessed with tractors at the time.