From Gary Chapman’s book, The 5 Languages of Appreciation in the Workplace:
Give a verbal compliment (Say, “Thanks for…”; tell them, “I’m glad you are part of the team”).
Write an email (“I just wanted to let you know…”; “it is really helpful to me when you…”).
Stop by and see how your colleague is doing. Spend a few minutes just chatting and checking in on them.
Do something with your coworkers, like eating together.
Do a small task for someone spontaneously (hold open the door, offer to carry something).
Stop by their workspace and see if they need any help getting something done.
Buy them coffee, a drink, a snack or dessert.
Get them a magazine related to an area of interest they have.
Give them a high five when they have completed a task (especially one that has been challenging or that they have been working on awhile ).
Greet your colleague warmly. Say something like, “It’s good to see you!” or “How is your day going?”