Assemble a group of young men. Five is usually the best number, and make sure they're as young as possible (under 25 years old is good). A rebellious one, a shy guy, an older guy and a younger one should definitely be included.
Learn dance steps. This is really the staple behind most youth bands today. If you watch a few instructional tapes and music videos, you should see it's mostly stepping and moving in sync with the music.
Practice singing at the karaoke bar. All you really have to do as far as singing is carry some form of tune. As long as the dancing and look is good the singing is just an accessory.
Find out if any member of your band can play an instrument. This isn't always necessary, but it can be an added bonus.
Put together some cool costumes and hairstyles for your band to wear, the flashier the better. Remember that the "good look" usually drives most youth bands.
Find one song you can all sing well, then sing it over and over. Once you have that one hit that will stay in people's ears forever, you'll be stuck in their heads too.
Put together a music video of your best song(s). Don't be afraid to overdo it on the special effects and fancy camera angles. The right flashy video can be your ticket to stardom regardless of how the actual music is.