I have some things I must add to this topic.
"Turn Etiquette"
You are free to do what you want to do during your turn, such as think aloud, calculate, check cards (with permission if it is the other player's), fiddle with your hair, or flick your cards to make the flicking noise that we all love and adore (it relaxes my nerves). But for the sake of the other player's competitive ability, refrain from doing any of the above during the opponent's turn, only checking cards when the other player activates like Poke-Power/Body/Trainer/Supporter.
During your opponent's turn: Relax. Leave your cards face down on the table to prevent the urge to flick them and put on your best Poker face. Picking at your face/pimples, snorting loudly, flicking cards, mumbling, or basically any excessive noise during your opponent's turn is rude and uncalled for. These acts may prevent the other player from making a clear concentrated move. Honestly, if I'm playing my Supporter and you ask to look at it after picking your face, I would provide a clear vocal "No" and request some proper etiquette from you.
You want to play in an environment where you can think clearly and make the right plays. Provide the same environment to your opponent during their turn.
"Volume"
Although this kind of refers back to etiquette, I felt it should be addressed in its own category. You should always speak in a clear voice, not necessarily loud. Be aware of your surrounding and who you're playing against. Sometimes, it gets a little loud so you have to speak up a bit. But if you're super confident in your attack and cannot hold in your excitement that you feel the urge to let the world know, you need to calm down. Be aware you might be yelling out your action to an amateur player, scaring the last remaining wits out of him and leaving him scarred, never attending another tournament.
Also, along with voice volume, there's gesticulative actions. Avoid flailing your arms wildly around the field. Pointing and picking up cards excessively is uncalled for. If needed, make some notes. Also, don't go swinging your arms when you call an attack or make some sort of gang sign when you knock out the opponent's Pokemon. And don't go slamming your cards onto the field either. Just politely interject or announce the arrival of the card.
These are just my 2 cents for this article. It's something I've been through (I've never actually played at a Pokemon tournament yet but I have been to other TCG tournys) and I would hate to see at the future Pokemon tournaments I plan on attending.
Feel free to change the wording if you decide on adding these to the original post rokman. Great article so far, I love it.