Hi, I'm new to speedrunning in general and I've decided to try Kirby's Dreamland 3. As a beginner to both speedrunning in general and to this game, is there anything I should know going into it?

If you go into the game blind I'd suggest running any%. The mini games and puzzles used in the game have some elements of RNG, and requires fast memorization. I run any% because a screw up could cost you multiple attempts at a puzzle. I'll link this guide so if you decide to run best end 97% it may help http://www.flyingomelette.com/faqs/kirby3faq.html