Bowser Jr's Robot Reactor
Grand Star #2
Lure the Bullet Bills into smashing the cages by standing in front of them and somersaulting (duck, then jump) at the last minute. Once Megaleg puts in an appearance, climb up one of his legs, dodging bullets and leaping over the moving cogs, until you reach the top. Lure another Bullet Bill to destroy the cage surrounding the Grand Star, and a fence will pop up. Now lure a bullet into destroying a section of the fence and then quickly guide another through the gap. The bullets are horribly prone to crashing into each other, the destroyed fence sections reappear after a short while, and if you die you have to start over from the very beginning. More than a little trial and error involved for this one, unfortunately. Grrr. Once you've lured two bullets into place, you can pick up the second Grand Star and open up the Fountain dome.
BONUS: Sweet Sweet Galaxy
Feed 400 star bits to the Luma next to the Terrace observatory to gain access to this bonus stage.
Don't you hate cookie cutter level design? Well, you'd certainly be forgiven for hating this one. It can be an absolute nightmare. Make your way around the moving platforms, avoiding the holes, and resist the temptation to jump unless absolutely necessary. It's actually easier to stay on the ground through this level, and nimbly run around the gaps, since it's all too easy to land in a hole with a badly timed leap. If you can, grab some more star bits and the extra life as you go. Climb the cake at the end and there's your star.
Space Junk Galaxy
Pull Star Path
Use the blue pull stars to make your way through the floating debris, using a little flick of the Wiimote to drop onto large objects. When you reach the structure with the insects, climb to the top and free the Toads from the crystals. Stand underneath the Starshroom and jump up to speak with Toad. Walk to the top of their ship and use the launch star there to move on. Now follow the walkway as it appears to find and rescue five Luma. Just walk slowly, and the blocks will appear as you approach. Once all five Luma are found, the power star appears back at the start of the walkway.
Kamella's Airship Attack
Just keep using launch stars to move from ship to ship. You'll learn another pair of useful tricks along the way - the high jump (jump then spin) and how to throw shells (shake that Wiimote). When you reach the ship that starts with a tall seasaw at the top of a mast, keep your eyes peeled for the blue pull star on the chimney opposite - you can drop down there for a massive star bit boost. As for Kamella, she's got two attacks - fireballs and green shells. Dodge the fireballs, and wait for the green shells to stop spinning before you try to pick them up (you won't lose health if they hit you, but they will knock you on your arse). Grab the green shells, and lob 'em back at her. After two hits she'll summon two normal Magi Koopas, so deal with those and then hit Kamella one more time to earn your star. There are coins on the front of the ship and in the question block, if you run low on health.
Tarantox's Tangled Web
As you've probably realised by now, many of the techniques you learn on the way through a level prove vital when tackling the boss. So it is with Tarantox. To reach him/her/it you must catapult Mario using the gooey sling pods sticking out of the ground. Walk into one, pull it back and aim with the Wiimote, then let fly. Ooh, that's fun. Once you reach Tarantox's web, spring Mario into the white mass in the middle to reveal your creepy foe. Then it's simply a case of flinging Mario into the creature's arse (nice) to knock it over, then twanging him into the three red nodules underneath. Tarantox will spew green bile as it shuffles around after you, but this is easily avoided or stopped by hitting the nozzles it comes out of. Knock Tarantox over two times and he'll tumble into space, leaving a star in the middle of the web. Twang yourself over there and get it. Job done.
BONUS: Yoshi's Surprise Appearance
On the way to Tarantox's Tangled Web, just before you drop inside the glass planet, you'll find a hungry Luma. Feed it 50 star bits and it'll transform into a wooden planet shaped like Yoshi's head. Use the new launch star to fly there, and then defeat all the Goombas that have made their home there. The best approach is to tackle them one at a time - keep moving, avoid groups, and take down lone enemies before they spot you. Be sure to kick them after you spin or hit them with star bits - they'll keep coming back otherwise. Once they're all gone, the hidden star is yours.