Hi,

We started DS1 at 2.5yrs as I wanted him TT before DS2 came along. We had great success and used a potty first then onto the toilet.
DS2 is almost a totally new thread!!
He is 3.5yrs and point blankly refuses to TT at all. Tried him various times. We are going to do just the toilet with one of those cushy seats. My DH made a small graduated step for the boys to use, it is stable for them to stand on when they need to learn to wee standing up.
There is a really good Toilet Training tips thread on here somewhere to help you with knowing if your DS is ready. I just can't find it right now..
Usally they need to be able to tell you when they have done a wee or poo or disappear when they are doing poo. Some kids will ask or just start taking their own nappies off themselves.

Good luck