“I would say the hardest job in the world is that of a stepparent,” says Susan Caso of Boulder Family Counseling. “They have to learn how to balance both their partner and their partner’s children’s needs and wants — that’s not easy.” Ask one of the 300,000 or so new step-dads and step-moms what the most difficult part of this already tough role is and many will come around to discipline. When a child acts up, as they are bound to do, how should a new stepparent handle discipline — without growing resentment in this new and fragile relationship? We spoke to the experts about navigating these tough waters. The good news: There’s a clear, if slow, path to success.

READ MORE: The Fatherly Guide to Step-Parenting

The first thing you have to look at is the age of the child. “All choices are made based upon their age when the stepfather enters the scene, the younger the child the more accepting of discipline they will be,” says Carl Pickhardt, author of Keys to Successful Stepfathering.

If the kid is young (0-9) it can be pretty easy to discipline them. They already are naturally inclined to obey adults and want to get along. Talk with them and point out what they are doing wrong and follow the normal rules of discipline.

For parents entering into a relationship with a kid who is older than nine, it’s important to realize that the child is already starting to separate from their parents as they try to find their own identity. “You need to be patient, have empathy, and understand that this is a trying time for the child,” says Pickhardt. “Assert your authority, but not in corrective measures. Instead focus on being someone who adds quality in their life, leave the corrective authority to the biological parent.”

ALSO: A Close Look at the Science of Step-Dads

While the relationship is being built both parents should actively work to involve the new stepparent in decision-making. To start, defer to the rules of the house that are already in place. Diana Weiss-Wisdom, the author of Wisdom on Stepparenting: How to Succeed Where Others Fail says a stepfather could say to the kids (in the mom’s absence), “What would your mom tell you to do in this situation?” The child responds, “She’d tell us to go to our rooms.” The stepfather could take a moment and then respond, “Then maybe you should do that.” Once the child starts to accept the new parent figure you can move into more traditional roles.

Eventually, the mother can send the child to her new partner to ask simple questions: Can Tommy spend the night? Can I go to the movies. For the dance can I stay out later? These should be questions the couple have already talked about in advance, allowing the new stepdad the chance to show they have some say in the household.

MORE: How to Discipline a Stubborn Child

With an adolescent, you can start to take a more active role in discipline in the household, but it takes significantly more time. “The stepfather needs to tend to his marriage first and support his wife. And from there, he needs to develop a relationship with the kids, as something like a coach or an uncle,” says Diana Weiss-Wisdom. “Over time, he can implement or encourage the kids to follow the rules that mom has previously set out. Privately, the stepdad can guide his wife with regard to the kids, but for at least two years, he should allow mom to implement any kind of rules or discipline.”

When time to discipline does arise, the key to success is communication. Have set expectations and consequences defined — write them down and post them so everyone knows what is expected. “If you set clear and concise boundaries beforehand then it removes the onus from the stepfather,” says Caso. “Say a teenager comes home after curfew, you can tell them that they knew what was expected and what the consequence now is.”

And be sure to listen. Stepparents need to take the time to talk with the child and find out what is going on with them before making a decision. Give the child a full hearing before making a decision and make sure they know you are listening to them.

“I have talked to a lot of kids that have stepfathers, and most say that they like them in their life,” says Caso. “It’s just that when the word discipline comes up they say that they want their mother to do it. They don’t want their step father to not care, just that they want to hear it from their mother.”

Read more of Fatherly’s stories on discipline, parenting, and behavior.