You’ve been hounding this donor for years.

You’ve tried every trick in the book: meeting request letters, letters of inquiry, cold calling, and even just sending that long-shot unsolicited proposal.

After one last desperate push, you finally get a meeting with him and guess what? He decides to give you a generous first-time gift! After years of hard work, your pursuit has paid off. Now it’s time to celebrate.

But wait. Though that first gift is cause for jollity, your work is far from over. When the donor signed that first check, there was no guarantee he’d sign a second.

After you finish that (well-deserved) glass of bubbly, your nose has to go right back to the old grindstone. Here are the first three steps you should take to ensure your aquatic friend doesn’t swim off again.

Get on the Phone ASAP

Every major donor should receive a thank you phone call within 48 hours of making their gift. A phone call, even if it goes to voicemail, is the most personal way to express gratitude and build the relationship (short of an in-person meeting, of course). Surprisingly and self-destructively, organizations procrastinate picking up the phone—and often don’t call at all. Don’t be that organization. Make the call.

 Grab the Nearest Pen

Many call thank you notes old-fashioned, but the donor will say they’re thoughtful. There’s no better way to start your relationship than sending a handwritten note personally thanking the donor for their support.

And if sheer gratitude isn’t motivation enough, the nonprofit Donors Choose found that donors who receive handwritten thank-you notes are 38% more likely to donate in the future. Just sayin’.

 Go On, Thank Them Again

It is nearly impossible to over-thank a donor.

Donor stewardship is a continuation of donor cultivation. When done right, it will make donors feel appreciated and draw them deeper into the life of your organization. Donor stewardship is not “keeping a donor warm,” checking in just often enough to tee them up for another solicitation down the road. It’s gratitude, it’s communication, it’s building a meaningful relationship with your donor. Make sure the donor feels your gratitude and knows that they are now an integral part of your mission.

Mail a welcome packet! Bring them into your donor club! Send an extra thank you email just because! Send a fruit bouquet! Okay, maybe not that last one, but never forget that donor stewardship is a relationship-long process, starting the very second the donor signs the check.

So, celebrate this major achievement by picking up the phone (and a pen and paper while you’re at it) and thanking your new donor (then thank them again).