I try to do little things where I can, whether it's mentoring to younger military members, helping stranded motorists (especially in winter) except when the wife and kid are with me. Or being the DD even when I could really use a few too many spirited beverages. People don't realize how good a simple "thank you" makes you feel.
Recently: Gave one of my younger buddies who just got married and moved into a new house a lot of my kitchen stuff. I'd gotten new stuff so instead of throwing it all away I probably helped him save a few hundred dollars. Donated about 6 trash bags of old clothes to a homeless shelter. And helped a buddy change his tire after his tire-iron broke in -20 degree weather.