I speak of your loyalty and your salvation. I do not hide your mercy or faithfulness from a great assembly.
As a child a phrase that was often repeated as a lesson was "If you don't have anything nice to say, don't say anything at all." Now as an adult, I see some flaws in that line of thinking but as a general rule, I think it is still a standard to aim for. Try to use affirming and encouraging words - you're bound to slip into negativity now and again, but overall, your words will be positive.
How would your life change if the words you spoke to and about God were words of praise for his loyalty, his mercy and his faithfulness? I'd bet the biggest impact would be on yourself. Yes, it would spill over to the people around you but by speaking of God's goodness, I guarantee you would notice more of God's goodness.