The horizontal speed of different sorts of movement are as follows: Shinespark > Grounded Speed booster = Jumping Speed Booster (Space boosting) > Running on ground = Rolling on ground > Falling spinning = Falling upright > Falling morphed > Crawling in Zero Suit.
Trying to just stay with whatever form of movement is the fastest is usually the best idea. The most glaring exception is Shinesparks, which have (relatively) a very long startup time and a lengthy bonk animation when hitting a wall, meaning speed booster is almost always faster if you can maintain it for the same distance as the shinespark.
Using this information we can create a couple of general rules to follow. Note that most of these have some exceptions, especially when there are more goals in play than strict horizontal movement, and for absolutely optimal movement you sometimes have to experiment, but following these will always be servicable.
Keep jumps small, spend as much time as possible on the ground Don't do anything special when running off a ledge, just keep holding the direction If you're rolling off a ledge morphed and intend to unmorph, do so early If you're going to perform a shinespark anyway, do it as early as possible Additionally, landing completely cuts your speed and will force you to accelerate to full speed again. So if a bigger jump allows skipping a landing where you would only run for a short distance (1-3 blocks) before being forced into the air again, it's not a bad idea.
Infinite Wall Jump is a tech that allows Samus to wall jump in a single wall infinitely. This is a very common strat in all categories.
To perform a Wall Jump you need to jump into a wall so that you're pushed against it, hold away from the wall and press the jump button. You can move back into the same wall to continue jumping infinitely.
You can wall jump off of a single tile wall so long as you can jump high enough to reach between the middle to top-half of the block.
This does not work when you have Space Jump.
When Samus is falling and in morph ball form, she will do a small bounce when she lands. This little bounce which costs a little bit of time. Whenever you are in a situation where you're not morphed and you start falling, and you want to be morphed when you land, it is usually faster to wait and morph as close to the ground as possible. This prevents the bounce animation.
In some situations it's not faster to do this, such as already being in morph ball when you start falling. In order to soft morph, you would need to first unmorph in the air and then re-morph near the ground. The unmorphing animation slows samus's falling speed a little bit, and loses the time you would save by soft morphing.
Place a bomb while morphed and stay within the bomb's blast radius, which is about a 3x3 size area around the bomb, and it will propel you upwards. This only works if you are still morphed when the bomb explodes.
Diagonal Bomb Jumps (DBJ)
Diagonal Bomb Jump (DBJ) Is a tech that allows samus to bomb jump diagonally, also with a determined rythm. You can also do both double Diagonal bomb jumps and regular bombjumps.
This is useful in Kraid, in 100% and in randomizers.
Jump Bomb Jumps (JBJ)
Jump bomb jump (JBJ) is a tech that will allow samus to jump, place bomb, and then jump and moprh into that bomb so she will bombjump from a higher spot. This potentially saves a bombjump.
This strat is very common in all the categories and is used to optimize bomb jumps as the technique in general reduces the required bomb jumps by a single bomb jump.
Infinite Bomb Jumping (IBJ)
Infinite Bomb Jump is a tech that gives Samus the possibility to bomb jump infinitely by placing bombs with a set rhythm. There are both double and single bomb jump variants, videos for both are included here.
This is used in tons of places, both in 100% and any%. This is also very useful in randomizers.
Horizontal Bomb Jumping (HBJ)
Horizontal Bomb Jumping is a technique that allows Samus to bomb jump moving left or right without gaining any height. This is accomplished by placing each bomb slightly to the side of the previous bomb. This is used primarily in the AWS room.
After getting the Power Grip upgrade you can grab ledges. You can press Up or A to climb the ledge normally once you've grabbed it, or you can do a input similar to a wall jump by pressing away from the ledge and A to jump onto it. In general it's slightly quicker to do the jump motion, but this runs the risk of missing the ledge grab entirely if you press your away input before grabbing the ledge.
A Shinespark is a tech that allows Samus to charge in 5 directions: The horizontal directions, vertically upwards or both diagonal upwards directions.
For the Shinespark to work, the player needs to speedboost and crouch, saving the boost. Then jump and press the direction of the spark.
Shinespark works the same way as speedboost so it will also kill enemies and break Speed blocks.
If Samus shinesparks into a slope, she can still running to the direction, making it a normal speedboost.
Restoring Speedbooster on Slopes
If you spark into an upwards slope while holding the direction you're sparking, samus will maintain her speedbooster and begin running on the slope. This is used in a lot of places to maintain a shinespark over a longer period of time. In some cases this tech is required by the game in order to enter some areas blocked by speedblocks, and in some cases it allows you to carry shinesparks into further rooms where they were not originally intended to be used.
A shine break is the technique used to break speedblocks on the ground that normally require you to run over them with a speedbooster and lose your speed while falling into the ground. If you perform a shine break, you will either crouch and store your shinespark on the first half of the speedblock tile such that it breaks and you keep your spark, or you've used a setup to run past the last half of the last speed block so that it breaks behind you while you keep running and store your shinespark after it.
Spaceboost is a tech that allows Samus to jump infinitely with Space Jump and a speedboost so she is Space Jumping at a very high speed.
To perform this the player just needs to run and get a speedboost, and then jump continually in air.
This also kills enemies on the way and breaks speed blocks, just as a regular speedboost.