I have a book that I want to get back into reading on blended families. As I read I'll post helpful ideas.
For now the number one thing I've learned is you must first establish a relationship with the step-child before you administer discipline or correction. If you don't have a sturdy foundation then that child will greatly resent any correction or discipline from the step-parent. Be sure to have some QUALITY time together. Take them out, just the two of you, and do something with them, get to know them. It's so different inheriting a child rather than growing with a child from birth.
For the biological parent...be patient and remember that if your spouse doesn't have a child already that they too will have to grow into this role.
Secondly, be sure to display the utmost respect for your spouse (the step-parent). Your child will pick up quickly on any resentment, bitterness, or negativity you hold against them. Kids are smart when they sense this they will sometimes use it to put you two against each other.
Lastly, if you have a disagreement about the way the biological/step-parent has handled a situation with the child then discuss it behind closed doors. If the biological/step-parent was wrong then approach the child and apologize. Pride certainly has no place in parenting.
Please post any of help you may have!!!