Learn some jokes. Especially clean ones. The dirty ones are usually funnier, but you need to play it safe. Tape some top comedians. Write the jokes down if you have to. People often say they can't remember jokes. That is because they don't immediately tell them. Practice at the office or with your relatives or anyone who will listen. You only need two or three good ones. Don't drag them out. Get to the punch line quickly. Tell it with animation. Watch the pros and learn.
You need to be familiar with popular culture. It provides useful small talk. It makes you appear informed and hip. Pay attention to current phrases. There is always a set of terms out there. "What's up with that?", "Hellooo" , "Work with me here", "Yada, yada", etc. There's a bunch of them and they go in, then out of style. Sometimes they can be juvenile, but it is a good idea to sprinkle some in your conversation at the right time. Be sure you get the context and meaning right.
Try to get familiar with a little bit about as many current subjects as possible. If would be helpful if you knew three or four of the most popular songs, shows, artists, etc. in each category. You don't have to be a fan of rap music or computers but it is helpful to be able to converse or at least recognize some important artists or terms. It's simply a matter of being informed. This does not require a lot of effort. Read a variety of magazines such as People, Time, Rolling Stone, U.S. News and World Report, Wired, Cosmopolitan (Yes, you want to know what they are into) and your local paper. Listen to several radio stations. Make it a point to know the top three artists in each music genre, top current films, actors, news stories, etc.