Tips for rapid improvement?

If you will come to my Event I will teach you how to improve your chess skills very much overnight.
Hi! Free Chess Set if you come to my Event! I can help! Just google this: "Learn how to become expert in a day tickets"

Most of the advice given previously is good. So I won't repeat it. Instead, perhaps think about and try to understand as many of the following tips/pointers as you can....it's a lot to think about, so if something doesn't yet make sense to you, move on to the next tip....
Pandolfini's 64 Commandments (of Chess)....
http://wcschess.co.za/sites/default/files/news/files/64%20Chess%20Commandments_0.pdf
And while there is not enough time for the following to be of use to you for your upcoming tournament, going forward you might want to consider studying a few instructive chess books...
Good Chess Books for Beginners and Beyond...
https://www.chess.com/blog/RussBell/good-chess-books-for-beginners-and-beyond
In fact, included in the list is..
Pandolfini's Ultimate Guide to Chess by Bruce Pandolfini...
https://www.amazon.com/Pandolfinis-Ultimate-Guide-Chess-Strategies/dp/0743226178/ref=sr_1_1?crid=1HP6VBTYLY67V&keywords=pandolfini%27s+ultimate+guide+to+chess&qid=1568340320&s=books&sprefix=pandolfini%2Cpopular%2C194&sr=1-1
the book is an excellent one to begin your chess studies; as you read it you will encounter discussion relating to items in his 64 Commandments.
Finally, browse this site; lots of good stuff there - you're likely to find something of interest. In particular I recommend to spend some time understanding what is on the following page....it's about maximizing the usefulness of your moves - a concept which can be put to good use immediately....
https://www.mark-weeks.com/aboutcom/aa06b18.htm

not one damn thing will help you improve in four days
not one damn thing will help you improve in four days
Sounds exponentially off
You still have not clarified what "expert: means.
My client
You are expecting people to spend hundred, and thousands of dollars, to become "experts" at chess.
duh!
BUT you haven't said what "expert" is?
MY CLIENT!!
Can you give some description of what someone can expect from this seminar?
THEY GET TO BECOME LIKE MY CLIENT !!!
The basics?
WHAT BASICS? WE'RE TALKING STATE OF THE ART EXPERT STUFF HERE !!!!
Comparable to a class D player? C player? B player?
EXPERT PLAYER!!!!! EXPERT!!!!!!
As the resident unsolicited solicitor, and for today only representing @ratingchess, please find the bunny's crystal clear explanations above in a pleasing legal orange hue.
not one damn thing will help you improve in four days
What is a logarithm?
not one damn thing will help you improve in four days
What is a logarithm?
although he might have meant algorithm

Unfortunately that is true and no different than the vast majority of threads on this site.
Mostly jokers and trolls having fun between bullet games. Good luck.
I came to this forum with the hope of getting some decent tips. There have been two useful posts.
Welcome to the chess.com forums. Where good ideas, help, and good posts, come to die.
What, so you're justifying your useless comments on every single one of my forums?
Mate, I've been grinding tactics, endgames, openings for hours each day. Just because all you see is the games I've played, that doesn't mean I haven't been studying other things. Why do you seem to enjoy crushing self confidence with your useless posts.
I remember asking for specific lines for 2.Bc4 - and you responded with a copy pasted opening principles post. I then asked for beginner tactical openings. You responded with a dissection of my worst games.

I remember asking for specific lines for 2.Bc4 - I then asked for beginner tactical openings.
Probably too late for your chess tournament, nevertheless perhaps helpful down the line...
Jim's Chess Channel on YouTube features good tutorials on some openings.....here the Bishop's Opening 1.e4 e5 2.Bc4....
https://www.youtube.com/watch?v=69en7ATGxnA&t=714s
https://www.youtube.com/channel/UChSqcu-VJQSLfQes1vlGL5g
Here, pretty thorough coverage of Bishop's Opening...
http://www.rci.rutgers.edu/~goeller/urusov/bishops/index.html
https://www.rci.rutgers.edu/~goeller/urusov/bishops/unusual.html
Finally, you might want to browse some of the stuff here on openings...
Chess Openings Resources for Beginners and Beyond...
https://www.chess.com/blog/RussBell/openings-resources-for-beginners-and-beyond

The info could be helpful in the future....but for the present, it might be like trying to drink from a fire hose!
Someday you may want to browse here.....my blog....stuff I've accumulated over the years (decades!) and decided to put it together for posterity on chess.com....the thought being that some may find something of interest....
https://www.chess.com/blog/RussBell

Hi! I've also been playing chess for around a year, and ive hit 1500 otb, and almost 1700 on here
Honestly, the thing that helped me the most was building an effective opening repertoire, and study tactics. Here's a link to a slideshow i made on tactics, I recommend you check it out when you have the time
https://docs.google.com/presentation/d/1SwDaRdfPd0IZHCEdiqr4aKFB5XNpzgcMQ2K3hVmT1CI/edit?usp=sharing Hope this helps
There is no magic pill for rapid improvement.
Asking for rapid improvement 4 days before a tournament is impossible.
This was a question you should have asked at least a month before the tournament.
The most useful advice i can give you is this...
Get plenty of rest,
Stop playing blitz, bullet, and rapid.
Do tactics.
Stay hydrated.
Eat a lite breakfast.
A cup of coffee 30 minutes before the round will get the brain going.
Avoid sodas, energy drinks, sugar, and sweets.
Have Fun!
This unfortunately is very bad advice. By far the best way to improve is to play lots of blitz. You can play 10 times as many blitz games as rapid games so you will see ten times as many endgame and tactics and will improve 10 times as fast

Try to play mostly longer time controls, including "daily" chess, so you have time to think about what you should be doing - blitz and bullet chess may be fun, but at this stage of your development they will do little to promote your rapid improvement or your understanding of how to play correctly.
It makes sense that taking time to think about what you should be doing would promote improvement in your chess skills.
This is not to suggest that you play exclusively slow time controls or daily games, but they should be the greater percentage of your games, much more so than blitz and bullet which do almost nothing to promote an understanding of how to play the game well. Rapid chess tends to be primarily an exercise in moving pieces around faster than your opponent while avoiding checkmate, in hopes that his/her clock runs out sooner than yours - this brings to mind the old TV game show "Beat The Clock"...
https://www.youtube.com/watch?v=zu0sZYGzWSs
Here's what IM Jeremy Silman has to say on the topic...
https://www.chess.com/article/view/longer-time-controls-are-more-instructive
And the experience of a FIDE Master...
https://www.chess.com/forum/view/general/how-blitz-and-bullet-rotted-my-brain-don-t-let-it-rot-yours