Stepmothers get a bad rap.  Lady Tremaine of Cinderella, the Queen from Snow White, Giselle Budchen: these ladies leave a lasting mark on the psyches of children.  In our culture, Stepmother = Evil.  That's a pretty tough hurdle for a woman entering a blended family.

And while it's never easy to go from "girlfriend" to "stepmom," there are ways to make the transition a little easier.

1.  Let go of expectations.  You most likely won't forge a close relationship with your step-children right away.  And that's OK.  We repeat, that's OK.  The children might treat you like a guest in their home, and you might feel like they're visitors.  You might never be close.  It will take time to figure out what your relationships will become.  Trying to view things from their perspective can go a long way.

2.  Never ask the child to call you "Mom."  Allow the children to address and introduce you by whatever they are comfortable.

3.  Butt out.  If their biological mother is involved in the children's lives, it is best to allow the father and mother work out any difficulties regarding the kids.  Your concern will probably be seen as meddling by the mom.

4.  Be clear on the family rules.  If rules are written down and vocalized, it will be easier to discuss the children's misbehavior with your partner.  Discipline should probably be meted out by the father, but make sure that your role is clearly defined by communicating with your partner.

5.  Be yourself, and be patient.  People don't respond well to phoniness.  Just be yourself, and allow your relationship with your step-children to progress naturally.  Don't push; you'll just push them away. 

And don't forget to read, read, read!  Here are some resources on blended families that can help you get through the rough patches.