Just do some googling - loads of info out there. Some bullet points for you, though:
- Nipple piercings commonly take between a year and a year and a half to fully heal, sometimes longer.
- They're likely to be tender for the first week and then get more comfortable; sleeping in a soft bra to prevent them catching on bedding is a good idea, and be careful with towels!
- Don't move/touch them while they're healing unless you're cleaning them.
- In theory this goes for boyfriends too, but I know that's a long time. Try to keep him off them for at least six weeks.
Also the usual; go to a reputable piercer, make sure the barbells you're pierced with are titanium, make sure the gauge of the bar is 14 (1.6mm), and keep a close eye on them as they heal for signs of migration. Follow good aftercare methods, DON'T change the jewellery too soon - it's probably the most common way people balls up the healing of piercings. Wait AT LEAST six months before changing the jewellery, and you should be fine.