Tournament Magic can be complex, with a lot to keep track of.  During a game, a player is allowed to make notes about cards they have seen played, or revealed, certain strategies they see used, or even what they plan on getting on their Sub after they finish the current match.
 
At the start of each match, when you sit down, your note sheet must be empty.  It also has to be visible throughout the match.  You don’t have to show your notes to your opponent, but he does need to be able to continuously verify that you aren’t sneaking a peek at something you shouldn’t be.  However, if a Judge asks to see or explain your notes, you are required to do so.  Any notes you take during the match may be referred to during that match, regardless of the game you are on.

Between games, you may refer to notes made before the current match.  It does not matter if the notes were taken 2 minutes before the match began, or printed off a website at home a week before the event. If they were in your possession prior to sitting for your match, you may review them between games.

It is very important to point out that you cannot access these notes during a game for -any- reason.  Even if all they contain is the Oracle text for your textless Cryptic Command.  The same goes for notes you took during a previous match against the same opponent.  Doing so, at Competitive or Professional level event, is a Tournament Error of Outside Assistance, and carries a severe penalty of a Match Loss, and at a Regular REL event, it will earn you a ‘Stern Judge Chat'(tm)
Additionally, players and spectators may not make notes while drafting or registering a card pool.

And finally, while some artistic modifications to cards are acceptable, modifications that provide strategic information may also count as ‘Outside assistance’.  Be sure to talk to the head judge to find out what is an is not acceptable before the event starts.  It’s best to find out before the event rather than during a deck check.

Today’s Rules Tip was written by Josh Stansfield, a judge from Orlando, Florida, United States.