NightLotus and I have done skits for 2 years, and had a first place skit at K-con 2009. I have some advice for new skits:
1. Have jokes that refer to your anime/game but make them also make sense to people who might not have seen/played it. People love getting the joke, and hate being confused
2. Have some fan service, but DON'T RELY ON IT AS YOUR MAIN PLOT
3. RECORD YOUR SKIT! The first year we didn't get around to it and our skit was a bit of a flop, but the second year we put some effort into making a good quality recording and that made a huge diffrence!
4. Have fun! This goes for your script, and your performance. The cosplay competition is really fun, and pretty easy going! Don't think of other people as competitors, and don't stress.
5. If you mess it up, don't worry! Last year I knocked off NightLotus's wig during the performance, but we just ignored it, and ended up doing pretty well! (If you want to see the embarrassing spectacle:
http://www.youtube.com/watch?v=-zGt6qIOUIs)
6. If you want to talk to me about writing or doing a skit, feel free to message me! I would love to help a new group get on their feet!