You can become a great conversationalist even if you aren't much of a talker. Personally, I have always hated small talk. Please don't talk to me about the weather, unless it truly is remarkable. Although I am not a fan of long conversations, there have been many times when I have found myself in situations with no way out. So I started to test out ways to become a great conversationalist and they actually work!
If you can learn to become a great listener, you will also become a great conversationalist. Most people love to talk about themselves so just make it a point to listen to what they are saying. Once you hear something that you can discover more about, you can ask them a question and this will build on the conversation. Don't just hear them, allowing what they say to go in one ear and out the other. Be proactive about it and process what they are saying to you; this is listening.