The art of a good conversationalist is to be a good listener. You will be far more welcome in a conversation as someone interested in hearing other people's stories, than in trying to push in with your own. If you want to tell a good story, there's nothing wrong with starting it with "A friend of mine told me ...." or "I heard a good story the other day ..." because it's the story that counts, not the ownership of it. Don't worry about your own stories being 'lame', make up for that by enjoying the two-way art of conversation. Conversation is about getting to know people - use a few stock questions - where do you come from / what do you do / children / hobbies etc. People love to tell you about themselves, and if you are genuinely interested, you will have good conversation, it's not all about the wittiest stories you can tell. Stick with these simple rules and you'll be welcome in any group, promise!