Damage Boosting is an important part of speedrunning DKC3 as it allows you to skip various sections of many different levels.
Here is some examples in "Rocket Barrel Ride" at 0:27 and 0:58
This is a useful trick that only works with Kiddy (unique to DKC3). You have to press B as soon as you land on the water to bounce off it (limit to two in a row).
Here is an example in "Tidal Trouble" at 0:08
Team Throw Hovering
This is a needed trick to beat Kaos the optimal way. In DKC3, if you time your throw right, you can hover in the air as long as you want and you won't fall like in DKC2.
Here is the example in "Kaos Karnage" at 0:25 Note: This trick does NOT work in the JP version.
Horizontal Rope Climbing
Unlike DKC2, you won't gain any time by jumping up vertical ropes. For horizontal ropes though, DKC3 is on fire! Kiddy being slower, Dixie climbs horizontal ropes like crazy and mastering this technique can be a real time-saver!
Here is an example in "Krevice Kreppers", the entire stage benefits of this neat trick!
Squitter Instant Platforms
These work differently than in DKC2. Instead of hitting L and R at the same time, you'll have to press L at least two frames before R so you can make an instant platform. In "Krack-Shot Krock", sometimes, you'll have to delay them ever more so you get the perfect level on each parts of the level.
Here is the example:
Team Up Jump
Press A exactly 1 frame after you press B and you will team up a slightly above the ground instead of on level ground. About a half second after you pressed A to team up, press and hold B on 1 specific frame to jump extra high. Use the sound Dixie makes when she jumps on Kiddy's back for the team up as an audio cue for the second frame perfect input.
Here is an example in "Ropey Rumpus" at 0:05 Note: This is sometimes referred to as the "2-1 Jump"
Krimp Just Defend
Normally, you can only roll through a Krimp from behind. However, by rolling at a Krimp from the front, and then pressing back immediately before you would take damage, you can kill him and continue your roll by holding forward again. This is called a Just Defend, named after the mechanic from Garou: Mark of the Wolves (which has the same input). NOTE: Although you can press back at any point during your roll to kill the Krimp, ideally you want to press it as late as possible to get the most distance out of your roll. Pressing forward immediately after he dies is also critical to maximizing the amount of frames you save.
Here is an example in "Low-G Labyrinth" at 0:23, which allows you to skip the comparatively slower jump over the Krimp.