remember that you are aiming your sales at kids and young teenagers, so make the music/hook/lyrics as basic and simple as you possibly can. Make sure that the people you hire to either star in your videos or mime along on TOTP (rip) are really hot so that viewers of all ages stayed glued to it. It has to be as bright and mesmerising as possible, to take away from the fact that the music itself isn't that good.
Finally, be aware that the music industry is fickle, and what's at number 1 this week will be old hat and forgotten by next week. Fast Food Rockers, anyone?