Paul gives us some great examples of the types of things that we need to be thinking about in his letter to Philippi. He says in chapter 4:8-9;
"Finally, brethren, whatever things are true, whatever things are noble, whatever things are just, whatever things are pure, whatever things are lovely, whatever things are of good report, if there is any virtue and anything praiseworthy - meditate on these things. The things which you have learned and received and heard and saw in me, these do, and the God of peace will be with you."
The important thing to remember is that the things that we think about are going to come out somehow whether in our actions or in our words. So if we're thinking about vulgar things are having thoughts of hatred - those things are going to find their way out into our speech or actions. We need to take Paul's words of instruction here and think and meditate on these things each and everyday.