How nice a thank you is.

You can never underestimate how much a thank you goes. It lets people know their work is not in vain. Further, it let's them know that they are a valuable member of a team. People want to work hard for those who value and appreciate them. You can get much better productivity from those who work with you if you are encouraging and thankful. 

So next time you are not getting all you need from a co-worker, rather than start with a complaint, be appreciative of what they have done first. Many rarely get a good word in this work-a-day world.  You may give the best word they hear all day. So give someone a lift today. You never know the productivity that will follow.