I don't know many, because it's my first jam, but I know three things:

1.  Do what you can before jam starts - you will need high amout(it's stylistically correct?) of time;
2. Do things you know - they won't take long;
3. Don't experiment(you can, but I'm not recommending to do it).

I'm sorry for possible errors, but English isn't my native language(it's Polish)

Hey I'm not the best at game jams, but here are tips I've found helpful from participating in ~10 of them:

1. Keep your scope small. Really small. So small the game you want to make almost feels beneath you. This is the best way to ensure you will actually complete a game. You can always expand your game later if you have time.
2. When coming up with designs for your game, come up with as many as possible at first and then evaluate them. Try not to jump at the first one that sounds good, but actually assess all of them as a whole. I've found this to be a really great way for determining what to work on and often I spend 1-2 hours during this phase.
3. Try to get a playable version of your game as soon as possible. This also helps with coming up with new ideas that emerge once you start playing your own demo.
4. Generally, try and make your artwork consistent. If you're making all your sprites 32 x 32 with a black border, try and stick to that. Throwing in a premade high quality pixel art asset you found on a store will look out of place. Also, I have found it helpful to stick to a limited color palette so you don't get bogged down with colors.
5. Leave time at the end for creating screenshots, gifs, and for exporting your project. You never know what issues might come up when exporting so try and finish up the project with a good hour before the deadline (ideally more).

Last thing I wanted to mention is going in with the mindset of wanting to learn and have fun. Focusing on just learning and participating with others as opposed to trying to win the jam has been a great way to feel good about the result, regardless of the result. As long as you learn something, it was a jam worth doing!

1-Straight idea acording the theme "It should be max 2 hours, usually take less time, also aproach this step for preparing your project setup".

2-Direct development of the most basic form of the idea "Coding main gameplay, doing art.. etc".

3-Complish "Start / End" that idea "After you finished it, use the last time you have left to polish as many things as possible".

4-Prepare your game as soon as possible to have early players with you, this also will help you with feedback from others "You might have some time to play others early prototipes, while step 3, you can release the main version before the polish final one!"

5-The moment you feel stressed out.. Stop and Chill, watch a movie.. Play.. or do something different to think deeply about the problem.  It works almost most of the times.

6-Celebrate!!! Finishing a game is a miracle that many devs would love to do, the more games you finish, the better you will get,

This are my honest tips! The ones that i use to finish my Jam games, also they work 100% fantastic in serious ones that includes team and money behind.

Hi! I made a few, here's my experience summed up: 
https://3dsfera.com/gjtips
https://3dsfera.com/gjchecklist