The basic idea is to encourage employees to reach out to each other in small, meaningful ways by providing business card-sized "connection cards" with messages of appreciation, encouragement and support: You are awesome. Your voice matters. You can do this. You rock.
The messages aren't all strictly messages of gratitude, but they are all expressions of positive attention that tend to inspire spontaneous gratitude. They make people smile, and feel cared for, which primes them to notice other things at work that make them feel that way.
The cards are inexpensive, and the actual messages can be customized to fit the needs and desires of the particular environment. In fact, an important part of implementing this project is talking with different stakeholders to see what messages they would like to hear in the workplace more often, and preparing them to deliver those messages more often themselves.
The backs of the cards are blank so that people can write short messages if they choose, explaining the specific reason for the card: "Thank you so much for your extra help yesterday." "I've really appreciated the way you've been running our team meetings." "Knock their socks off tomorrow!" Etc.
I've found that putting messages like these in writing has a much bigger and longer-term impact than simply speaking them. (There are people who still have cards taped to their monitors, or in their wallets, that I gave them years ago!)
To get these cards used across an organization, it seems to me that employees need 1) to have easy access to them, and 2) to be actively encouraged to use them.
For the easy access, I envision "gratitude stations" in office common areas that would have a bunch of connection cards and pens, envelopes and stamps (for sending cards to people in other locations), and maybe even candy or other small gifts that could be attached to the cards. In addition to providing materials, seeing these stations could help people remember who they would like to reach out to, and prompt them to do so.
I could also envision providing a way for individuals to order their own sets of cards, if they have many opportunities to give them to people and/or don't have easy access to a gratitude station.
Active encouragement is important because offering personal messages like these can feel weird and make people feel vulnerable, especially when few other people are doing it. Employees need to see why it would be worth their time and the emotional risk of trying something new. Ideally, the organizational leaders would go first, experimenting with connection cards themselves and publicly sharing their experiences, leading by example.
I would strongly advise against any kind of external incentives or rewards for participating, because its the voluntary nature of the giving that makes it so special and meaningful. Not to mention, cards are simply not everyone's "thing". Let people participate for whom it feels good, and if other people are inspired to encourage and thank people in different ways that feel more authentic to them, that's great! Because ultimately, the goal isn't a lot of pieces of paper being passed back and forth, but a workplace environment in which people authentically trust, support, and appreciate each other.