This is a topic dear to me because I end up talking a lot at work..:)Being a project manager, my role requires quite a lot of interaction - tons of emails, frequent meetings with teams and phone calls. I am not sure about others but for me, it is very easy to loose mindfulness once I am off cushion and deep into daily routine. It is specially difficult to be mindful while talking to others since the process demands an instantaneous reaction to what some one says. I can do better when I am reading and replying to emails or doing something on my desk by myself.
Incidentally, I was doing some digging into sutta pitaka and came across "The Abhaya Sutta", http://www.accesstoinsight.org/tipitaka/mn/mn.058.than.html. This is where Buddha is talking about speech to Prince Abhaya and basically he is saying that one should be careful to only say things that are factual, true, beneficial, and endearing & agreeable to others. At times something could be factual, true, beneficial but not endearing & agreeable to others and for this, he advises us to wait for the right time to say such a thing. A simple formula but so powerful! I think most people do try to say factual and truthful things most of the time but how many of us think if it is beneficial to the listener? Endearing & agreeable being even lower on list. If we can be mindful of these simple attributes, how much effective can our speech be!