Other People's Children - The Pitfalls of being a Step-parent or "Uncle"

This week the MadMen analyze the pros and cons of dealing with a man or woman when they have children. How do you deal with other peoples children while dating, when thinking about getting married, when tying to discipline? How about dealing with the other biological parent (aka baby momma/daddy drama)? If you are single and have children, how do you know when to trust someone else around your children? Do you introduce the kids to every man/woman you date? Do you consider how they treat their own children a factor bef