Pick your best talent and believe in it. Talent show contestants arrive believeing that are good at what they do, no matter what it is.
Make your talent distinctive. If it isn't distinctive, talent give it a special twist that will awe the spectators. We can't all ride a unicycle around an obstacle course, but if you play an instrument or sing you can create a creative arrangement of a popular song to play to show off a little more and get a crowd response.
Go all out. Dress up like an actor and do an involved impression, complete with jokes and props. Create a juggling routine and perform it to a mix of favorite songs. Put on a puppet show with contemporary themes and puppets you've created. Don't just exhibit your talent, embody it.
Never underestimate how weird you are. Talent show spectators love to see bizarre talents that seem straight out of the world record books. Don't do anything dangerous, but don't hesitate to expose those crazy skills you have for fitting marshmallows in you mouth or doing a quick chocolate syrup painting. If everyone else is tap dancing and singing the national anthem, you'll definitely stand out.
Continually practice. Consider the things that might go wrong and eliminate them. Test out any props or technology that you are using and have a back-up plan in the event that something fails. If you can, keep props to a minimum so you cut the chances of mishaps.
Never underestimate the power of crowd response. If you're not that talented at something, go with your best skill and play to the crowd. Make eye contact and give the performance everything you have. If the crowd laughs at you (when you're not trying to be funny), laugh with them. Everyone loves an underdog, and your sheer desire and pluck may win them over. If you can get the audience cheering for you, it can sway the judges.