look up hitboxes, learn all the characters and switch to a different one if you stop improving with one. read everything you can about advanced techniques and practice them, especially z-cancelling and teching. find friends who want to get better too and play against them at least a few times a month. experiment with what is possible on the controller, and read through the 'simple things you may not know' thread for tips. practice fluid platform movement on dreamland with all the characters, learning how each one can use different techniques and jumps to most efficiently navigate bottom to top, bottom to side & side to top. (luigi's up + b or full neutral jump will get you bottom to top nicely, for example). don't forget about shorthops, instant double jumps, stick jumps and neutral vs. sideways jumps as options. practice all your platform movement and z-cancelled aerials between stocks, and play vs. a cpu level 9 to practice combos rather than to win, like someone said above. also in general take items off, use 'a' a lot more than 'b', rarely use shield or roll and when you get crushed in a tournament ask for advice about what areas of your game need improvement. training mode for combo practice, cpu 9 dk for combo implementation. worked ok so far for me anyways that's about how i improved.