Read his cues.
My oldest trained at 3 fully from day one of training. We tried at 2.5 with no luck. He just was not ready. When we tried again at 3. He has had 4-5 accidents since day one of training 3 months ago. He was just ready.
My 21 month old is ready now and starting. I am not as aggressive with him because he is still young. I suspect he will be fully trained before his 2nd birthday.
My training tips.
-NO diapers period. I do not believe in going back and forth or diapers at night or when you are out and underpants during the day. It is just confusing.
-Pullups are just glorified and over priced diapers. I did buy a pack for my son. However, we only used them OVER TOP of underwear as a back up. We did this for a couple nights and on our first couple outings. He actually wore the same pair at night because he didn't pee. I still have the whole package minus the 4 pairs we use. I think that if you just put on a pull up it is no different than a dipe. It actually took A LOT of convincing that they were not diapers and special night night underwear when we used them those few nights. He knew they were diapers.
-I started with him sitting down. It was just easier to teach him to sit at first, especially since he needs to sit for #2. Once he was fully trained, I introduced standing up to pee. When he stands, he likes to make pee bubbles in the water. Never tried the cheerios, but would have if needed.
-Lastly, take his cues. If you are struggling he probably is not ready. Boys do take longer.
Anyway, sorry for he book. Just my observations on PTing my son earlier this summer.