There still are some rules, and they're useful from time to time.

People starting out want to break the rules and usually come to grief.

A good one to keep in mind is Principality. One idea should stand out above all others. A fashion picture usually has a heirachy of ideas but despite the brilliance of the participants (hair, MUA, stylist, photographer) a competition of ideas is usually not percieved. Rather only when some or all are trying to be geniuses does the whole thing crash, usually because the rule of principality is broken. (Is it a hair, beauty or fashion picture)?

Poor lens choice and model posing can break the rule too. The hand on shoulder that's too close to camera becomes as large as the face and competes with it for attention especially if the fingers are spreadeagled in a fan-like shape. A normal lens shooting full figure at eyeline makes the legs look short and the upper body large. The picture takes on a principality thats unwanted.

With Photoshop the big idea can be forced onto the picture. Most internet forum pictures suffer from a serious lack of post production, which incidentally is the name of the game right now. Emotional principality, ideas that weren't concieved at shooting time can be added later after some thinking.

A good example is found here: http://www.showstudio.com/projects/comme/production.php Nick Knight's pictures for Comme des Garcons.

Knight breaks the rules in the best way; he simply doesn't accept what he ended up with pre post production, and uses all the post production re-touching expertise suppled by Photoshop to get what he's after. Strangley enough he ends up with the principality he was looking for.

But the "rule breaking" if that’s what it's called comes after the taking and in the post production. To be succesful at this you need to be working from a big sample which is probably part of the difficulty. The shooter doesn't have it because he doesn't want it. He wants to be different. It's been said the only truly different people are eccentrics. I've yet to meet anyone who called themselves an eccentric fashion photographer. But if too many rules are broken when starting out that'll be the result.

The team supply it in the shooting stage and hopefully the viewer will get it at the looking stage. The photographer, MUA, hair and clothing stylist all contribute to this but now added is Photoshop. Not just for re-touching but for final picture editing also. Photoshop stamps its look on the final result and can maximise the emotional investment of the 4 other players.