I was fortunate in that I didn't experience any bruising after my nose job, and only mild discomfort. That may be due to the skills of the surgeon, but I also did some preparation beforehand.
I read a few articles on minimising bruising and the common themes were to take Vitamin C, Zinc and Arnica Montana, as well as staying in general good health.
I started taking Effervescent Vitamin C and Zinc tablets from Tesco everyday for two weeks before surgery and for ten days afterwards. I also took Arnica tablets(6c) from Holland & Barrett two days before surgery and for five days after.