Try as soon as you can after delivery. I had a csection, but still kept trying a few hours after delivery.
It's awkward at first (actually for the first few weeks.

), but keep at it.
Since I wasn't having much luck in the beginning and worried that my baby needed some milk, I had a lactation consultant come in and help.
She was soooo great and creative. We coaxed the baby onto the breast and slid a tiny tube filled with formula along side of my breast into the baby's mouth. This was great because it eased my worries of the baby getting milk, but also helped the breastfeeding latch.
If you want to bf, just don't give up early. It takes a while for mom and baby to figure it out.
Some people may say not to give the baby formula or that the baby doesn't need milk until it can latch on to your breast... do whatever you feel comfortable with.
As for knowing when they're full... you might not in the beginning since they're really just trying to get on and drink. But eventually once the baby can latch, they will stop drinking when full. You will know when the milk comes... you will hear the baby gulping and see that he/she is drinking.
Good luck...