Do something that the child considers special. For example, a stepmother shared her stepdaughter's passion for movies. They began attending the cinema then stopping for hot chocolate and a discussion of the movie before heading home. It was an experience the girl cherished and one she hadn't had with either of her natural parents. Present a united front with your spouse.
Children learn how to play one parent against the other.
In the stepfamily, children may claim unfairness or insensitivity on the part of the stepparent. The biological parent may be tempted to side with the children. No matter how much you disagree and have to thrash parenting matters out in private, you and your spouse must present a united front to the children. This will minimize playing one of you against the other. It will make you more creative and effective because you will be working as a team.