For example, today I was working on bringing up a system and it just wouldn't work. The servers kept spitting errors at me instead of doing what I wanted.
So I asked for help. One of the server guys came over and very politely looked for a minute or two and pointed out that - due to my previous messing with the system - I had managed to get mismatched versions on there. He told me how to fix it and left.
(Fast forward about 45 minutes)
I got the system up, having made the recommended changes. Awesome! I'm done here, right?
I wrote a note to the guy who helped me. Just two lines it said, "Hey, that fix worked. Thanks for the pointer." And now I'm done.
The important part here is that I followed up. It took 30 seconds of my time and about 10 seconds of his (to read it), and now no one's wondering what happened, or if the problem was fixed, or if I was too busy to even notice that someone took time out of his day to help me. In two sentences, we've resolved all doubts: yes, it worked; yes, I notice and appreciate the help.
It's small, but it makes life around the office a bit more friendly.