You post a topic, list, category, whatever, in my comments section. (examples: "5 Sexiest Things About Ron Weasley" or "Top 5 things to drink"). Then, in a separate post, I'll post the answers to all your Top 5 ideas, according to me. Then you post this offer in your own journal.
And now I rest safely in the knowledge that no-one ever answers to my meme-posts anyway. :P