I think I liked D2 year more than D1 year. A little more studying, but at this point you know how to do dental school already. For me, each year was better than the previous in dental school.
So, do D2 year just like the same way you did D1 year. It's not all that different.
But if you are wondering what it was like, I think at our school it was either 23-26 credits per semester.. Lots of lab based courses, and it was a little more dental focused than D1 year. If you want to be at the top of your class, it sucks because you will have to sacrifice sleep and social life a bit to make it happen.