I've played some matches where you must first move and then write down what you played. It is the best way of analysing a match.
Tournament Rules.

http://www.fide.com/component/handbook/?id=124&view=article
Rule 8.1
You must first move and then write it down. You may even reply a move first and then write both down.

Are you more concerned about fide or uscf rules ? They sometimes differ. I believe fide now requires you to play the move first and only then write it down. You should be able to find fide rules online, as well as uscf rules.

I'm actually concerned about FIDE and the Canadian rules (CFC) ...
But if FIDE requires you to move first, and then write it (what a STUPID rule!!!) ... I assume the CFC requires the same thing. Although to be honest I'm just gonna write it first anyways until a TD tells me not to :) ... they aren't gonna forfeit you for something like that (right away :P).

I just read the rules of FIDE concerning recording of moves and it doesnt seem to say you must first make your move and only then record it. It does say you may not make a move without recording your previous move however. Its not really very clear, the way its written imo. In any event , I have always written my move down first and then done a "blunder check" before playing the move on the board and will continue doing so until I am told by an arbiter that its not allowed. I do not see how this is "cheating" in any way.

Why wouldn't you follow the rule ???
It's not stupid, it prevents cheating.
Preventing people from bringing pocket fritz to a tournament "strictly for annotation purposes" and then carrying it with them to the bathroom "so it doesn't get lost" is how you prevent cheating. Stopping someone from writing their move down (on their own time!) and 3 seconds before playing it doesn't stop cheating :).

I play USCF and write down my move before I play it all the time. I can't imagine it being illegal. I know that if you have a Monroi that you cannot write it down before you move, because then you can actually see the resulting position.

I play USCF and write down my move before I play it all the time. I can't imagine it being illegal. I know that if you have a Monroi that you cannot write it down before you move, because then you can actually see the resulting position.
Senior USCF TD Here.
All players in official USCF tournaments (I cannot speak for Canadien rules, I don't direct events in Canada) are now required to make the move, and then write it down - consistent with FIDE Rules (references above). However, in many USCF tournaments, the TD will still "warn" players for infractions instead of forfeiting them for writing it first and later moving. The rules change was to stop folks from writing down the move, studying the board, erasing that move and writing another move and then studying the board... you get the idea... while very very limited, it was decided (not by me, don't shoot at me for this), that constituted "analysis" and was not allowed by the rules to analyze.
(( personally, I think: "If you cannot hold onto the first move you contemplate in your brain, feeble you." and Tough Turkey. )) Officially, I went with what the organizer directed when directing tournaments last year. that was: warn them once. Once was always enough.

Ok, that link made it more clear than the one I read. It also states that both players are required to note any draw offer(s) on their scoresheets. I have never done this and havent noticed others doing so. Do you , as a player, note draw offers on your score sheet ? I will try to start doing so.....IF I can remember to .
The rule was changed recently so that you cannot write a move first. I play a lot of tournament chess and for me it is no problem if my opponent writes the move down first. I do get a little annoyed if he then thinks for a while and crosses out the move then writes another - that I think is the practice that the rule change was intended to stop. Also did you know that you must also use algebraic notation? descriptive or English notation are also forbidden. i am quoting the FIDE rather than USCF rules. And if you write the move down first and your opponent complains? Probably a warning from the arbiter then a forfeit if the offence is repeated.

That's good to know. I have a Monroi, so I don't have that problem. I can't tell you how many times I wrote down a move and then realized that it would have been a game-losing blunder earlier in my career. Silman even recommended in his books. If people have a problem with me writing down a move before it is played, then they are just WAY too paranoid. I am not saying it is you, but writing down the move just brings you back to the moment to where you can adjust your viewpoint.
I've heard different answers to this among masters... I wish someone could actually SHOW me the rule.
This applies to Tournament OTB chess ... Are you allowed to write your move down first and then make the move, or must you first move and then write it down?