Whether a job offer is a dream come true or a dream deferred, most employees react in similar ways when presented with a formal contract: stunned, happy, and relieved. After all the anticipation, everything is finally in writing—or about to be.

But what happens next may surprise you: You accept! Congratulations! Not so fast. Before jumping ship, consider whether staying put might be more appealing than taking this new opportunity after all. In some cases, it can be wise to turn down an offer and present a counter offer letter instead.

Here’s how to do that effectively:

1) Take time to weigh your options
Weighing pros and cons can help you gain clarity on whether this new opportunity is the right fit long-term and whether you’ll ultimately be able to fulfill both your responsibilities and potential in this new setting. It can be helpful to consult trusted advisors such as mentors, former employers, and peers for advice on what would be a good next move.

2) Craft a solid counteroffer
Consider all of the factors that were important when choosing between offers: compensation, benefits, work location, expectations of the position, and any other details that were included in one or more job postings. During negotiations, it’s important to know your value—and theirs. What are they willing to do without? What is their “walk away” number? Can you meet somewhere in the middle?

3) Recognize timing
No matter how confident you may feel going into counter negotiations, remember there is a “right time” to do so. During the interview process, you want to make sure that all of your cards are on the table and ask questions such as: Who will be my direct reports? How is compensation determined? What does it take for an employee to advance in this organization? What is the company culture like?

The strategic negotiation process depends on time and timing. In general, it’s best to wait until there is a job offer in hand before engaging in any type of negotiation. Don’t forget to include a timeline for when you would expect hiring decisions to be made and when you would need a written contract from your new employer.

4) Understand what makes an effective counter offer letter
You don’t want just sound bites—you want facts, figures, and metrics that support your bottom line. And you’ll need to provide this evidence in a way that’s ranked high enough in someone else’s mind that they can back up their decision with data as well. It doesn’t have to be complicated, but it should be solid.

For example, if you are looking for more money, you might say something like: “I’ve researched the average salary for this position in our region, and I believe it is $X.” Indicate that you’d like to confirm your expectations by sending an email summarizing your research (including the date).

A counter offer letter should be well-reasoned and professional rather than emotional or angry. Keep it short and sweet—an attention span is short these days! You want them to act now; you don’t want them to think too much about it because now is when they’re most likely to make a decision based on emotion versus reason.