Wispy-Stage: I like to do this level first because I find it the most difficult to do really fast. At the start, tilt the ball towards the middle (don't let it hit anything) and let it drop all the way down as fast as possible. Then hit the "trampoline" at the bottom at the right moment to jump back up to the top. Then try to either hit the spot inbetween two of the shrooms to get the ghosts out or fire the ball gently to one of the upper corners and let it drop onto them. If done correctly, you can get one or even more bounces between them and get rid of them really quick. You can also use the tilt buttons to get easy double hits on the "shroom-ghost-things". Just make sure to hit the remaining one before the others reappear. To hit the star then, you should try to hold the ball, release and fire it just before it rolls off to get a quick shot straight to the corner without hitting the edge or an obstacle. You can even get the ball through the frog without rolling in from the corner using the tilt buttons, but it seems to be much less reliable.
Wispy-Boss: The quickest boss to kill of them all. Try to let the ball slide down the slope and hold'n'fire it straight up. If done correctly, you can then mash tilt (B-Button or Right, depending on which side the ball is) to get one hit on the boss per tilt. You have to be careful with the setting because apples or the spiky thing can get in your way. The spike is on a fixed timer with two fixed spots while the apples have multiple spots with a random pattern. If you miss the quick kill, you can still hit him normally and just use ~30 more seconds to beat him. Just make sure to not fire right into his blow attack because that will most likely send you right into the star.
Kracko-Stage: A stage with a good time save potential. You can just drop down and shoot back up with the trampoline like in the Wispy stage, but since we already use this for Wispy, you would need to lose a life first since the second trampoline is already too short to be able to fire you to the top floor. Instead, I just fire the ball straight to the upper right corner because the "angry cloud" - which you have to hit 3 times - is about to arrive there and you can get the ball kinda stuck between the solid item spitting cloud and the angry cloud to land 3 hits instantly. Use the tilt buttons to adjust the ball if needed. Then the angry cloud will move towards the big Kirby in the middle. While that happens, I try to get the ball down and hold it with any of the flippers. As soon as Kirby brought out his umbrella, I release the ball and shoot it straight at the solid cloud. The ball should bounce off it to the top, bounce again at the ceiling and land perfectly on the umbrella. Once the ball gets shot to the top floor, I try to fire it immediately to the top left corner. That will most likely hit the sun at least 2 times, sometimes even 3. If you hit it 3 times and the last hit bounced the ball off to the top again, you can even hit the moon a couple of times immediately, depends on the collision with the stars. If you didn't kill the sun directly, be careful to not shoot right into the little guy in the middle because he will often send you straight down on a hit from below.
Kracko-Boss: Here you can save lots of time with good aim. It's hard to explain this, you just have to react properly to the action happening, but I always try to hit Kracko from above by bouncing off a wall first because then I can use the tilt buttons to adjust the ball in the air and try to land double hits on him. It's also a lot safer than hitting him from below because you have more time to react with the tilt buttons if you see the ball takes a bad curve right into the star. The hits from above get even easier as soon as you land 4 hits on Kracko because then he grows bigger, has a larger hitbox and moves a lot slower and more predictable. However, if you miss a hit on him, make sure to use the tilt buttons to hold the ball in the air or move it towards the other side or directly to your flipper and hit it since Kracko will try to freeze one of your flippers and it lasts pretty long so the ball rolling down the side with your frozen flipper is bad news.
Poppy-Stage: An easy stage to get to the top floor. The hole is quite big so you can just fire (or hold'n'fire) the ball at the beginning to shoot it up.Try to hold the flipper on the side where the ball is going afterwards since the ball will bounce on that flipper directly on to your other flipper. It can be a bit tricky to shoot the ball right up since the little guy on the right will have dropped the bomb already so make sure you don't hit it when using the right flipper. Alternatively, you can just hit the left kirby as soon as the ball arrives as the cycle is perfectly set for the squid to come out. Just make sure to not bounce too far off or you might hit the hungry kirby who will eat the squid. On the top floor, there is one thing to take car of.. the CHICKEN... it jumps into your way all the time so try to carefully play around it. You might also try to hit it on purpose 4 times so get the beetle item for safety. For the eggs, I try to shoot the ball towards the middle one and drop down onto either the left or right one to get two hits right away. Then I try to focus on these eggs so they won't be renewed. After all 3 eggs are gone, it can be a pain to hit the star. Try to use the time the last baby chicken needs to walk to the top to get the ball down and hold it until you shoot it when the star is halfway down and before the bomb gets in your way. I try to use the right flipper since it seems to be more reliable (but that might just be my preference). Again, make sure you time your hit with the chicken that still stomps around.
Poppy-Boss: Again, good aim is the key here. Try to hit the ball early if it rolls down the slope or you hold it to not hit the blocks instead. As soon as Poppy splits up, make sure you time your hits so they never throw two bombs down at the same time. You can use the tilt buttons to your advantage to wiggle the ball around if you get onto the little blocks to get multiple hits on Poppy (or the Poppies).
DeDeDe: First hold the ball until DeDeDe has fully spawned then try to release and hit the ball early to get a bounce off to the left instead of hitting him from below and risk the ball to fall straight down. You can also get two hits per flip if the bounce to the left was strong enough to bounce back on him. After 5 hits, he switches to the second phase and aims straight for the ball. Just try to let the ball gently roll up a slope and get DeDeDe right in front of it. He will get hit several times and just bounce the ball up by itself. Alternatively, you can hold the ball with your flipper and wait for DeDeDe to hit it, but sometimes you'll lose the ball so be prepared to tilt the ball the right way if needed. After 8 more hits, the third phase starts. You'll want to get as many double hits on him as possible by hitting him from above while he is standing still. Try to not hit him too quickly after the first hit beacuse he has some invincibility frames after a hit. Optimally, you also cancel his move to freeze your flippers with that. If you miss a hit, try to plan when your flipper gets frozen and tilt the ball the right way. That can be tricky especially if he stops in the middle. After 10 hits it's over. Try to minimize the way for the ball to fall into the star by tilting it.