Super Mario Galaxy 2/Hightail Falls Galaxy

Hot-Stepping Dash Pepper
Cross the bridge with the Paragoomba on it and get Yoshi out of the shell. Climb up the wooden slide along the trail of coins and grab the Dash Pepper there when you see it. This will let Yoshi blaze up the slope and across the platform to the Launch Star at the end.
 * First platform

This platform is mostly vertical and is split into three lanes in the beginning. It's easiest to go right up the middle, but there is also a ? Coin on the left that will create a trail of coins for you to collect and you'll need them to feed a Hungry Luma later. Halfway up the platform the right side will go up a hill and you'll need to dodge the Paragoomba there. If you take the more dangerous left route, you'll be rewarded with another Dash Pepper that will let you get to the very top of the platform where a 1-Up mushroom and a special character are. If you took the right path, you'll end up at the next Launch Star, otherwise you can jump down to it from above.
 * Second platform

Grab the checkpoint flag and start heading down this platform. The stone sections will drop away once you've been on them, so keep moving. When you grab the Dash Pepper you'll need to be careful not to run right off the edge. You should keep collecting the coins in the center of the platform if you want to feed the Luma up ahead. If you speed wears off at the end, you may need to jump and flutter kick to make to where the Launch Star is waiting. Off to the side of the Launch Star is a blue warp pad to a time trial filled with Paragoombas. This is a good spot to pick up some extra coins for Luma, and maybe three 1-Up mushrooms if you have time.
 * Third platform


 * Fourth platform

Here you can grab a checkpoint flag and another Dash Pepper, then run up the blue ramp and take the wooden wall to the right and down another ramp. Be careful not to run into the poles along the way. Cross the bridge and you'll find the Hungry Luma past the Dash Pepper. Give it 30 coins and it'll open the planet with the hidden star on it. If you're not doing the hidden star, grab the Dash Pepper and go up the ramp, across the moving platform and along the wall to the right. Go up the wall in between the purple blocks and you'll see the Comet Medal in the corner. Head left at the Comet Medal along the wall and down to another blue ramp. From here you can take the pull flowers on the left over to the next platform.

At the bottom of the blue ramp where the Dash Pepper is, you can see the Power Star above and to your left inside some purple walls. What you're going to do is use the Dash Pepper to go up the wall and circle around counterclockwise and run straight into the gap where the star is. In the top left corner of the wall there is a 1-Up mushroom, but it's very hard to grab and not fall down, meaning you'll probably have to go back and try the wall again if you go for it. Don't hit any walls and you'll make it easily. If you crash right next to the star, flutter kick or jump off of Yoshi and spin to try and save it. You'll want to take that last corner really wide so you can turn enough to get back up into where the star is.
 * Fifth platform

Hightail Falls Speed Run (Prankster Comet)
In this speed run, you'll have three minutes to finish the course while meteorites are falling through the sky wrecking the platforms. Don't stop for anything and running into something while you're on a wall with Yoshi is going to be a major setback. The meteorites made holes in the platforms and there are no safety rails this time around, so be especially careful about where you're going, and if a Smeech latches onto you, just shake it off. There is a 1-Up mushroom where the Comet Medal was on the first star, but it is inadvisable to get it due to time constraints. If you don't make any major mistakes, you can easily get to the last platform with over a minute left on the clock, so take you time doing the last platform to make sure you get it right.

Silver Stars in Hightail Falls (Hidden Star)
In the middle of the fourth platform, right after crossing the wooden bridge, you'll find a Hungry Luma who wants 30 coins to create a new planet. Take the pink Launch Star over to a small grassy planet with Kleptoads running all over it. Five of the Kleptoads are carrying silver stars and you need to collect them all to make the Power Star. Just run around with Yoshi and eat all the guys you see. This is a very simple star to obtain.

Green Stars
The first Green Star is at the top of the second platform. Stay all the way to the left so you can grab the second Dash Pepper and make it up to the top. The second Green Star is on the other side of the purple walls where the Comet Medal was on the fourth platform. Go left at the purple walls like you're going to continue on the course, then turn straight up the wall and jump off the top just to the left of the purple walls. Flutter over to the right so you land on top of the purple walls, then walk over to the edge and jump out the star. Sometimes you'll get a huge mega jump off the top of the wall if you jump at the right time, so just flutter kick and look down to spot the star and drift over to it while doing flutter kicks to slow yourself down. The last Green Star is above the pull flowers in between the fourth and fifth platforms. Swing off the flower to the right of the topmost one, then flutter kick to the right and finally jump off of Yoshi for the last boost to get you the star.