Fantastic advice all around!
On the vaguer, more subjective side of things, I'd like to emphasize intent, too! Really bugging with what your game's supposed to deliver. It's easy for the intent to be "To win!!! With the beast greaphics!!! Amazing cutscenes and the most fun gameplay" but that's extremely intangible. So perhaps a good tip for a jam is to try to cook down the experience to extract the richest flavour from that core idea, that core vision that precedes the desire to win. And that also means that even if you "lose" - meaning, you don't earn one of the prizes, you still have the biggest prize, which is the ultimate coalescence of your vision. Invaluable! Incomparable. And potentially worth hundreds of times the prize pool, if I do say so myself. (If any of the RPG Maker bestsellers are to go by, the one thing that unifies them seems to be the passionate dedication to their core idea. Even the humblest ones like my personal favourite Helen's Mysterious Castle, which I do think saw only modest sales, but that will forever be one of my most beloved games of all time :) )