First, I just want to say that it is totally possible for you to go the distance this time around!!!

Be determined!
1. Does your milk come in sooner after you give birth with the 2nd baby?
I am not sure about this. My boys are 20 months apart and I nursed #1 until he was 16 months, he self-weaned. My milk came in RIGHT away, but I figure it was because I only didn't nurse for 4 months and then had a newborn that was nursing, nursing, nursing. Literally, I am going to say that my milk came in less than 24 hours after birth.
2. Are there things I can do to help establish a good milk supply right from the start?
Nurse, nurse, nurse. Follow the baby and not the clock. Nurse on demand. Don't allow for pacifers or supplements. Also, I want to add that it takes until the baby is nearly 6 weeks of age for your milk supply to fully establish, so it is VITAL to nurse on demand that entire period.
3. How often did you nurse your baby after you delivered and were in the hospital?
As often as they wanted to. The first month definitely no longer than 2-3 hours between the start of one nursing session to the start of the second(you time nursing sessions like contractions from start to start). Heck, the entire first year of both my sons' lives I nursed whenever they wanted to. BM is meant to be the primary source of calories and energy for the first 12 months of life. Anything else is inferior.
4. What advice do you have for successful nursing.
Nurse on demand. Don't listen to outside opinions about nursing on demand. Contact your local LLL for support now while pregnant and then attend meetings with your baby after it arrives. Support is so vital to successfully BFing for 12 months.