What kind of speech do you have?

You brood of vipers, how can you, being evil, speak what is good? For the mouth speaks out of that which fills the heart. The good man brings out of his good treasure what is good; and the evil man brings out of his evil treasure what is evil. - Matthew 12:34-35

What does your speech consist of? Is it foul language? Perversion? Or is it the things of God? Do not be deceived, whatever is coming out of your mouth is what is in your heart. God sees all of it. You can't fool Him as you fool yourself. It's who you really are when you aren't putting on a mask to create a show for the public. So many people fill themselves up with perverted and foul entertainment, that is the food you are feeding yourself on, of course it's going to show up in your speech. What about the "friends" you spend your time with? Do they help you cultivate a godly character or are they just perverted and foul and are the very people the Bible tells you to stay away from?  

To change what is coming out of your mouth to good things, you need to first repent (turn from your sins and towards God) and put your trust in Christ to save you. Then you need to fill yourself up with good food. Read your Bible everyday. Listen to sermons from great preachers. Read books from wise preachers. Spend your time with friends who have godly character. Soon enough you will see that what is coming out of your mouth has changed and is now good speech because you have filled yourself up with good things.