Take time to express gratitude - thank the grant program staff. They have spent a lot of time providing technical assistance to applicants, and reviewing and evaluating your application, even if you did not receive an award. A thank you leaves the funder with a positive impression of your organization, which helps build relationships. Going old-school and sending a snail-mail, handwritten thank you note goes a long way!
Thank entities that provide letters of support too and follow up to let them know whether the project received an award. Even if the application wasn't successful, let them know you appreciate their support. Building relationships fosters collaboration for future grants and inspires other entities to help you meet your goals.