Boundary predators are easy to find at work. They include the boss who asks you to work the weekend you have a family wedding or the client who tacks on two more presentations to the senior team than you agreed to, or the team leader who assigns you more work than your colleagues.

Boundary predators aren’t just at work. They also include the crafty four-year-old who says, “But Daddy said I could have another cookie!” Or the 17 year old who commits to driving three friends to the movies without first asking your permission to borrow the car. Or the beloved partner who leaves the dishwasher for you to unload even though you made a deal to take turns and you did it yesterday.

Boundary predators rely on their power and authority — and your passivity — to get what they want. It’s up to you to push back by understanding how to create boundaries and maintain them. Personal boundaries are difficult to define and hard to maintain in all spheres of our lives. Unlike laws or national boundaries, personal boundaries don’t exist on their own; you have to will them into existence through conversation, especially if you aren’t in a position of power. However, all kinds of people conduct these difficult conversations every day with customers, clients, and kids, clarifying the work to be done and both drawing and holding the line. The following approaches will make it easier for you to conduct persuasive conversations that set and maintain boundaries:

[Here are four.]

Have an Agreement Up Front

When everyone consents to terms ahead of time, everyone knows what the objectives are and what to expect, and there is usually less potential for opposition. For example:

• “I have to leave this meeting at 11:30, but I’ll check in this afternoon.”
• “Yes, you can take the car, but you will have to be back by 10:30 so I can take your sister to practice.”
• “Let’s say that you can always have two cookies, but only two cookies, for dessert.”

Establishing a clear boundary gives you a defense against withering in an endless meeting or listening to continuous nagging for more dessert. Then, you can just remind the other party of the agreement and be firm. “Only two cookies for dessert, remember?”

Mention Your Credentials

Setting boundaries, no matter how casual, requires some authority. Briefly referring to the expertise you bring to the table gives you additional power in boundary negotiations. Here’s what that sounds like:

• “I’ve worked with at least 20 CEOs in similar situations, and I know I can help you.”
• “Yes, I’ve worked with this software on several other projects, and I know I can make a contribution to the team. But we’ll have to figure out how to reassign my current work.”
•  “As your father, I am responsible for your safety, and I don’t think that’s a safe thing to do.”

To up the ante a little, mention others who are with you:

• “You’ve reached the right department to resolve your problem. We have a reputation for being the best, so if you follow my instructions, I’ll have you back online in a jiffy.”
• “Parents choose their kids’ TV programs, and your dad and I agree that’s not a program you should watch.”

Expect Your Boundaries to Be Challenged

We’re all familiar with “scope creep”— when you’re asked to do more than you signed up for. As any parent of a two-year-old knows, setting a boundary is almost an invitation to test it. So, don’t get angry. Think about it and make a choice. Do I want to make this an exception or do I want to stick with the agreement?

There are times when you can gain something from conceding, but you’ll need to reset the boundary bargain as a part of the same conversation. For example:

• “I’m happy to do it again for you, this time. How about lending me two people on your staff while I do it? I’ll teach them all I know, and then you’ll have the resources in house.”
• “Yes, you can have the car all day Saturday if you drive your sister and her friends to practice. The following Saturday, though, I’m going to need it.”

Ask Questions

Ask loads of clarifying questions before committing, especially when you aren’t clear on the right approach. The answers will help you decide what to do when your boundaries are challenged. Keep your questions open-ended, so you’ll be able to gather more information without being perceived as negative:

• “Let’s talk a little more about your project. You said it had strategic importance. How is that? Do you have some ideas for the outcomes you want? Let’s come up with some options for meeting your team’s strategic goals for this fiscal year.”
• “What can you tell me about the people we’re creating this how-to-interview program for? Are they experienced interviewers? What concerns do you have about their ability to select the right person for the job?”
• “That is an interesting new bike you want us to buy for you. What makes it different from the bike you have now? What do you plan to do with your old bike?”