First of all, you to decide whether you are replacing a few items of your office or want to upgrade the whole equipment.
After that, you should get information about the charity organisations working in your area or town which will help you to select a particular organisation that needs your office equipment.
You will find many charity organisations working in your city or town and these organisations usually manage homeless shelters, animal shelters and many other relevant services.
Contact to the public relation officers or other people in the management of these charity organisations and ask them if they need your office equipment.
You can take help from internet for finding different charity organisations in your area and their contact details. It will help you find all details of non-profit or charity organisations working in your area. Just contact them or visit them and let them know that you want to donate your office equipment.
You can also call to the local Salvation or Goodwill Army store and let them know that you have office equipment and want to donate it. They will let you know if they are accepting that kind of equipment. Army stores usually sell the equipment and the money goes to the charity organisations.
If you are replacing the furniture of your office and want to donate the used furniture then you can contact to the furniture bank of your area that usually divide furniture equipment to different charity organisations.
You can also visit Help1Up.org for finding a furniture bank in your area. They will donate your furniture to different charity organisations because their staff members always remain in touch with furniture banks.