1). Never take on the role as sole disciplinarian, follow the lead of Mom. Ask her how would she would like you to support her, while taking note of her style. You should not be expected to raise the child alone, but are there for guidance to both Mom and child.
2). Take your time. Don’t rush to replace the other father. Most times the father is still in the picture, if not, proceed carefully and ask the child if they would like to participate in any activities with you.
3). Allow your wife/significant other to spend time with her child(ren) without you being present (especially in the beginning). It signals security on your part and helps to communicate that you are not there to replace anyone.
4). Create new family rituals like vacations, dinners, sporting events etc. that will slowly replace past rituals. Step-children feel threatened when they are excluded and these activities will go a long way in easing their insecurities.
5). When the time is right ask each individual child to spend one on one time with you, take them to places like coffee shops, ice cream parlors etc. Never to a movie, amusement part or other distracting activity. Use this time to get to know the child by listening.