I am playing in the Manhattan Open tomorrow, what should I do to prepare

What can I do the night before that will help?

Sleep.

I mean seriously... for a big open tournament you do all your prep in the months or weeks leading up to it.

The night before there's nothing left to do except be well rested, being in a good frame of mind, that sort of thing.

It's not different. They post a pairing sheet, you find your board, you sit down and play, try to find some food before the next round, etc

Good luck on your tournament! :-)

Now, the day of the tournament, I like to do stuff like solve some easier than usual tactics. Just to get myself in a calculation frame of mind without much work.

Or set up a board, and play over some GM games with little to no analysis. Again, just to get used to doing some calculation and looking at a position.

This.

A few days... or even a week or two... isn't enough time to make any changes to your game. The most you might do is confuse yourself. Spend the time on physical and emotional preparation instead.

Get a good rest. Eat well. Spend a few hours doing something you're good at, to build up some confidence.

Notice that among the 2000+ rated respondents... myself, Preggo, Mickynj... the opinion is unanimous: use the time to rest and eat well, not to study new lines.

Sit on your hands.

Seriously.

The idea is that before making a move you will need to pull your hands out from under your butt... and that action should (once you get into the habit) remind you to spend a dozen seconds on one last blunder-check before moving.

IMO the main difference between speed chess and OTB tournament chess is in tournament chess you're actually doing analysis... this means choosing between two (or more) moves.

In blitz, it's usually enough to validate 1 candidate move is OK, then you play it.

In a long game that's just step 1 (assuming it's not a forcing win).
Now you have to find at least 1 other reasonable move and check it too.
And finally as the last step you choose between them (whichever one is better).

And then yeah, like blueemu is saying, right before playing just look at the most basic forcing moves to make sure it's not a blunder one last time.

I agree. But OP, please don't think they are all wrong now!

And if you're going too slow, then think of it like... maybe like spending money. Where is a 5 or 10 minute think the most valuable?

Is it finding the difference between which rook to put on d1? Maybe the engine would tell you figuring out the right one is worth 0.10 pawn.

Or is it during the inevitable critical position where the difference between best and 2nd best move is huge.

I guess that would be my main point to slow players... is that in 99% of games you're going to get some critical position that will require you to make some tough decision. Plan on at least 1 or 2 a game, and save your long thinks for those times.

If your problem is you play too fast, I'd say remember to have more than one candidate move. As Lasker said, when you find a good move you should stop and look for a better one.

Yes, they are all right.

(When can I become a 2000 plus player!)

Listen to Preggo. He know his advice

Good luck in your tournament!