1) Don't post an offer to drabble more than once a day. 2) Fill every request, unless someone has asked for something from a point in the show you haven't seen yet (I suggest making it clear how far you know the show if you really want to volunteer to write for a fandom you aren't fully into yet). 3) Tag your post with your username. That way, if someone wants to find all the requests you've filled, they can do so easily and go on a binge reading your drabbles.
Rules for Requesters:
1) If you get a drabble, thank the person that wrote it for you. Common courtesy, people. 2) Don't request more than one drabble per person offering. You can give multiple choices about what to write, but only make one comment. For example, if two people post on Monday, you can make two separate requests, one for each person that posted. You cannot make two requests of the first person, and none of the second. 3) Only request stuff you actually want to read. Don't try to gross out writers for the sake of it.