How do you stop dogs from barking?

I usually go to see what my dog wants, or have him sit with me, other than that, the barking doesn't happen. The funny thing is, my dog doesn't bark a lot of times, but when it does happen, I am always given clues as to whats wrong. For example if my dog is waiting by the door I know it's time to let my dog out, or, if my dog is alone barking I know attention is needed. I think the subtle hints is what get's me through the barking.