I like to always make sure everything I build has some unique feature within it personally, but what rules do you follow ?

every block is the dash spider part

i try to represent every single sound in the song with something in the level, i built a part with like breakcore drums but slower and each kick, snare and hat have all some pulse in the level design. not doing that is the reason why a lot and i mean a lot of levels feel disconnected from the song.

if you want to see a level that does this in the best manner i recommend Orchid Sprite by ImmaxX1

That anything I make I should be proud of and try my hardest to put in something unique or something I haven't seen yet in my levels.

the level should be more forgiving than the player realizes. basic game design rule that most people fail to follow

Never make a level without a goal in mind. I must clarify that this is very anecdotal; in fact, many people claim the opposite, that you should just build without thinking about it too much. This has never worked for me. I need any level I make to have an idea, a concept behind it, which motivates me to keep building, if only to carry out the concept to completion. This could be as simple as "a level in XYZ creator's style", but it has to be vivid enough to propel you forward.

dont be afraid to scrap parts!!!! you can always make something better

having standards is OK, but i think it's fun to just build shit that you find cool instead

maybe my tastes are skewed but i always find random cool levels ambitious children built a lot more fascinating than like, mythic worthy levels by established creating titans
the child doesn't adhere to any standard, they just built what they thought of in their head, and that is So cool! meanwhile i feel like a lot of highly established creators aim to produce stuff that's visually compelling...Which seems a bit more laborous if that makes sense

Sorz i'm yapping here but... I guess it is a topic im passionate about
I wouldn't say that the established creator has absolutely no fun, I just think they sometimes feel the pressure to "preform" when it comes to creating a little...If you wanna make a level parodying an old trend, do it! I've got a level parodying sweetdude!
And it's fine if it's "a massive drop of quality" or "unratable" ... You had fun building it, and that is really all that matters :)

Focus on music representation and atmosphere instead of immense details.

do something you like without feeling pressured.