First, don't ever forget you didn't give birth to them. Never refer to yourself as their parent, don't tell them what to do or act like you think they are pulling a fast one when you get home and they are doing something wrong. Act stupid and vaguely confused; don't act like you have any idea of how to raise a child. Apologize for your lack of intelligence, make sure you have plenty of extra money and find ridiculous reasons to hand your stepchild cash. For example, pay them for expressing a preference for a certain type of apple. Hand them at least ten dollars and suggest it's for something they did that you can't remember but you're sure you owe them money.
Avoid anything resembling a direct command. Say things like: "Oh, are you watching a rerun of Laguna Beach? I bet that's really helpful for getting that paper on the Constitution done." Smile constantly.Don't act like you are a friend because you aren't; you're the least effective adult in this child's life. At lunch time your stepchild will exchange stories with his peers about what a dim bulb you are. The lunch you rose at dawn to construct will be analyzed and laughed at.
Don't write little messages to your stepchild; they will be read aloud and sneered at. Do not allow your stepchild to take pictures of you and don't leave affectionate messages on their cell phone (which you persuaded their real parent to allow them). Those messages will be played on the speaker phone and parodied by your stepchild's friends.
Here are your pet names: Loser, poser, moron, freak. Don't think anything you are doing, the laundry, the ironing, the shopping, and the car payments have altered your status at all. Don't try to teach them how to drive or offer any advice. Nothing you do will have a positive affect. Learn to walk silently like an Indian, flatten yourself against any receptive surface when they are near, never, ever introduce yourself to their friends; you don't have a name. Apologize before you ask them anything and be sure to stress you are only trying to help. They will hate you anyway so it doesn't matter.
If you take them shopping, prepare for passive resistance. Hours will pass while your stepchild silently accepts the clothes you suggest, smiling sweetly. Then she will stand in the dressing room making faces to indicate what a total waste you are. When you call out sweetly to inquire whether she needs a different size or color or a zipper zipped or possibly a kidney or your car, there will be a long silence. You will hear whispering and recognize she is on her cell telling her best friend about the terrible way you treat her. Don't, under any circumstances, suggest she show you any of the clothes.
Just accept her rejection, hand her the charge card and leave. When she comes home with a leather mini and a t-shirt that says SLUTBITCH in florescent letters across the chest tell her father you think she looks fine. "What are you talking about?" he'll roar. "She's a child." Exchange glances with your stepchild but be prepared for betrayal. Be prepared for her to tell her father that you wanted her to buy the shirt and while she felt cheap, she wanted to make you feel less useless. "She can't help how stupid she is," you hear your stepchild say in a high sweet voice, the voice her father has downloaded onto his computer. "She doesn't know me."
One day you come home early and find your stepchild in pain. He has had a bad day at school and hates his teacher. You make him a grilled cheese sandwich and tell him about how badly you failed Algebra. Twice. You bake chocolate chip cookies and leave the nuts out because he doesn't like them. "I'm good at math," he'll say proudly, "Like my real mom."
You nod and smile and don't make any snide remarks about how his real mom can't be all that great at math or she'd stop forgetting his allowance and the dates of his school conferences and what size shoes he wears. Later you overhear him telling his father about his bad day and he alludes to your sandwich.
"She's a good cook," he tells his father. "She melts cheese really well."
One day you forget they are not your children. One of them says something mean about your husband and you snap at them. They stare and you don't apologize. One of them has a terrible disappointment and without thinking you put your arms around her and whisper into her hair how sorry you are. For a moment, you are simply a family.