Toad Circuit
Time to aim for: <0:30.000
This track is relatively simple in its strats. For the most part, just drive carefully and you should be fine. The biggest issue is avoiding the boost panels, so you don't fly off the track. The way I do this is by aiming for the white surface to the left, and hugging that wall, as shown: The other issue you might find is getting stuck on the wall in the tunnel. To prevent this, try to keep your speed low and take a tighter line. Everything else on this track is simple driving. Don't hesitate to reset on this track in your attempts if you make any major mistakes, since it's so early in the run. For the sake of thoroughness, I'll also be including this shortcut, but do note that it is NOT viable in runs, to our current knowledge: This shortcut takes advantage of 9999cc's high speeds in order to skip right over the out of bounds. Unfortunately, this makes it very luck-based. This, combined with its difficult setup, makes it not worth attempting in real runs, especially considering how little time it'd actually save.
Daisy Hills
Time to aim for: <0:42.000
Most of this track can be easily completed with careful driving. The only problematic thing is the boost panel before the glider, which can be easily avoided with a well-timed hop.
Cheep Cheep Lagoon
Time to aim for: <0:40.000
This track is where things begin to get difficult. Water physics especially can be difficult if you don't know what you're doing. To prevent random speed boosts, you should always hold downwards on the circle pad, so that the kart is tilting upward, whenever accelerating. This goes for every water track. To start off, once you get to the boardwalk, fall off of it on the left. Once you land, use the bump to gain massive height, allowing you to fly over much of the track. Make sure that you are holding downwards on the circle pad while doing this. The other obstacle in this track is the cave at the end. There are many ways to approach this, so don't hesitate to experiment with it on your own and see what works for you. In the video shown here, I get some air while entering, and aim to the left to avoid the stalactites. Another option is to go in with a high speed, and clip through any stalactites in your way.
Shy Guy Bazaar
Time to aim for: <0:40.000
This is yet another track with a few options for strategies. We'll begin with the faster one. Begin with a weak rocket start, and carefully drive through the track until approaching the hairpin turn section. Here, you must clip through any nearby wall to your front or right, aiming slightly to the right. If done correctly, you should respawn just before the ramp with the boost panel. If done incorrectly, you're placed in a good position to try again. From here, just continue to accelerate forwards until you respawn after the glider, and from there you can finish the lap normally. It is possible to not fly off the track at the end, but it's quite risky and not worth attempting for so little time save. One other thing to note is to be careful when starting each lap, as missing the bridge is a costly mistake. The alternative strategy is to aim for a good respawn at the start of the track. This can cut off some driving, but is generally a little slower compared to the first strat when well-executed. This respawn is most consistent on lap 1, since there is a clear cue. When attempting on lap 1, try for a strong rocket start, and aim for the furthest lamppost. For laps 2 and 3, you'll just have to ballpark it, or go for the first strategy.
#N64 Luigi Raceway Time to aim for: <0:36.000
This is one of the simplest tracks in the game. Realistically, you should be able to nail a solid time here without any strategies. Simply drive carefully and don't fall off, and you should be fine. However, if you're looking to shave a few seconds here, there are some things you can do. Firstly, at the start of the track, avoid the bump. This bump gives you airtime which will make it much more difficult to control your movement. The second and more difficult strategy is to clip past the tunnel, skipping it and its somewhat slow entry. None of these strats are necessary for a top time, but if you're feeling confident with them, feel free to go for them.
GBA Bowser Castle 1
Time to aim for: <0:33.000 This is yet another simple track. Drive it normally for the first few turns, then attempt the 150cc glitch, as shown in the video. Aim roughly for the middle of the wall, slightly angled to the left. If done correctly, you should land among the boost ramps, where you have no choice but to go forwards and respawn. Aim slightly right to finish the lap, and repeat.
This guide is a work in progress, and I'll add to it when I have time and feel like it.
I hope this helps, and if you have any questions, feel free to join the discord on the sidebar and ask away, we'll be happy to help.