What should I do to prepare for an OTB Tournament?

Nice! Glad to hear

Write down all moves immediately. You are no longer allowed to write your move in advance as this was deemed to be an aid to memory (which it was in my case).

Remember that an upside down Rook is NOT a Queen.

Here is a link that will help you: https://www.chess.com/blog/teju17/magnus-forgets-a-rule-to-lose-chess-rules-you-arent-aware-of-teju17

So you always must make a move, then write it down, correct? (In settings where notation is required.) I've heard various stretches of this rule but I want to be sure I'm following it exactly. 

Yes and if there is a draw offer then that must be recorded as well.

Definitely wait til after u move to write it. Touch the clock with the same hand u move with. Use one hand to castle and ALWAYS move the king first when castling because ur opponent CAN make u move only the rook if u touch it first. 

Glad ur gonna play otb rated chess, it's way more fun than online. Many on here don't know what they're missing.

Where was this heard? My local chess club also hosts USCF rated events and an upside-down Rook is a well recognized "Queen" upon promotion. Perhaps FIDE has different rules on this, since USCF only applies to U.S.A. players? I thought for sure FIDE rules also accepted an upside-down Rook to act as a promoted Queen if needed.

It happened at a tournament a few years ago and now a spare Queen is provided at matches and tournaments and is supplied with new tournament sets in the UK.

If time permits another Queen is usually to be found at tournaments although we cannot leave the board if it is our move so finding another Queen when promotion seems certain is a good idea.

On chess.com, a Arena tournament is better than swiss tournament 

How is this relevant to anything? 

More questions from somebody hoping to play in his first* tourney later this year:

One needs to bring one's own scoresheets?  

*not actually first.  I played in two USCF tourneys 50 years ago (yes, to the best of my recollection they were both in 1971).  Back then, scoresheets were not required (that I remember).  I might have written my games down on notebook paper.

scoresheets are usually provided, but some people choose to bring their own as well. In events where notation is required, then the "official scoresheet" is the one they provide and you turn in after the game - but some people like their own scoresheets for personal archives. 

Some events also provide scoresheets where there is a thin layer so that your pen goes through the paper and you can record the game twice (each layer). One being for the "official scoresheet" to be turned in and the other for yourself if you want it.

The only thing you need to play is:

-yourself

-membership for organization

-event entry fees 

-I also like to bring my own pens, but they are usually provided with scoresheets for those who need them.

-some people bring their own chess sets and/or chess clocks as well, but this is usually optional as there are typically many available by host(s) the event.

Thanks for that info.  I've been fantasizing about playing in the US Open. (https://new.uschess.org/121st-annual-us-open-championship)   Are there a decent number of under 1400 players that would compete in that?

Also -- another newbie-ish question: if they provide scoresheets without the "double copy" thing, and then you turn it in, how would you ever have a copy of your own game?  Surely those tourneys don't expect you to record each move twice, do they?

I would think there would be an opportunity to record the game on your own copy afterwards.. they hold on to them anyways, so I would think you could ask for it after the tournament too. 

Depends on the event. Bigger events like the State Championship I played in last year will have the "double copy thing" but as for smaller events like your local chess club, they might not require you to turn in the scoresheet or if they do, then you'll have plenty of time to copy the moves by hand if you wanted them. 

As @cvjdbkgxc mentions, you could probably ask for it afterwards too - but I wouldn't 100% guarantee this option - I'd just copy it by hand after your game ends before the next round.

p.s. this was USCF, but I don't know about FIDE notation rulings - probably the same I'd guess.

Also, another tip when you're at an OTB tourney- Be firm on your point if there's an argument.

Once I moved my king BUT didnt press the clock. So the it was still not a complete move. But my opponent played his move without waiting for me to press the clock. So I called the arbiter and said that my opponent had played without waiting for me to press my clock. according to fide this was an illegal move. But the arbiter said he did it by mistake and to move on. If I had been firm and called the other arbiters and had argued, I would have won that game! But stupid me, kept silent and lost that game. 

So, If you feel like the game was unfair, do not keep silent!

Score books are not allowed in some federations as they may be used as an aid to memory.