Plinking
Plinking, short for "Priority Linking", is a fundamental technique to getting the most out of your combos. It makes difficult combos much easier to achieve.
The Technique
Plinking is done by inputting two consecutive buttons exactly one frame (1/60 of a second) apart. It sounds a lot harder than it really is. However, it is typically very difficult to perform on controllers apart from an arcade stick because of the button layout and design on most pads (i.e. standard Xbox/Playstation controllers). The catch is that it only works if a higher priority command is input before a lower priority button.
The Mechanics
This technique exploits a mechanic in USF4 that gives certain commands priority over others. The formula is relatively simple: medium attacks have priority over light attacks, heavy/hard attacks have priority over both, and kicks have priority over punches. The priority list looks like this:
LP < LK < MP < MK < HP < HK
Plinking allows you get an extra frame to hit the next move in your combo, which makes the notorious one-frame links entirely possible. There are two reasons to use plinking over attempting to hammer the same button twice within 2/60's of a second. One, it is almost physically impossible to do so. Two, the game will not recognize the same button press on two consecutive frames, as it interprets this as the button being held down. A button must be released before it can be hit gain, so the fastest possible mashed input would occur every other frame. Thus, it wouldn't be useful for attempting a one-frame link even if you could physically do it.
The technical explanation for the existence of plinking is most likely to make button combinations like throws, focus attacks, taunts, and EX moves more lenient. In games like SF3: 3rd Strike, it was not uncommon for players to fail an attempted EX special move because they hit the two attack buttons one frame apart. Plinking repeats the first input on consecutive frames and allows the system to register the second input of the higher priority command. When done successfully the inputs should appear like this: 
Notice how the first input is registered twice? This is what adds that extra frame to the one-frame window used in many difficult links. Because of the priority system, the lesser input (MP) is ignored in favor of the higher input (HP). This principle applies to any input and any combination of inputs, allowing for a large amount of plinking possibilities.
You can only plink a LK~LP when crouching because Throw takes priority while standing. You cannot plink MK~MP or HK~HP because Focus Attack and Taunt take priority at all times. LP has priority over nothing, so it cannot be plinked by normal means (more on that later).
Double Plinking
This technique is a plink that utilizes three buttons instead of two. It helps make a plink successful if the timing of the first input was a little off. It does not give an extra frame, it simply increases the plink's chance of succeeding. This is because it acts like you plinked twice.
True Double Plinking
The difference between regular double plinking and "true" double plinking is true double plinking actually involves two different plinks in rapid succession. This further increases your chances of hitting the one-frame link. It acts somewhat like an option select, but depends on your timing rather than the opponent's response. An example of this would be adding a MP+LK plink to a HP+LP plink. If you somehow miss the timing on the first plink (HP+LP) the second plink (MP+LK) will come out. This can be useful if you're having trouble with certain links.
Blinking/Slinking
This bizarre plink involves the use of the Back (Xbox) or Select (Playstation) button, thus Blinking or Slinking. The Back/Select button is secretly the lowest priority input in the game, effectively having priority over nothing. Its usefulness is derived from its unique ability to double any input or any combination of inputs, giving an extra frame to each and can essentially plink the combination rather than the individual inputs. This includes light punch (which was previously impossible to plink), grab/throw, and ultras (3-punch/3-kick buttons). This is very useful for trying to do strictly timed throws, or even kara throws, ultras, and anything else. Unfortunately, this technique is not available in Trials mode, as Back/Select brings up a menu screen displaying the combo notation.
On arcade cabinets, the Start button serves the same purpose, although the location of the button can vary to the point where it becomes impractical. Blinking/Slinking is not possible for 3DS users, since the Select button acts as a second Start button. The slink will register and come out if done correctly, but at the cost of momentarily pausing the game. It is therefore not a reliable way to practice the technique, nor is it good to use in online matches.
Kara Canceling
In Street Fighter 4, some moves can be canceled very quickly into another move which gains additional properties it otherwise might not have had. The cancel has to be done 1 frame (and only 1 frame) after the first move is inputted, and this type of cancel is known as kara canceling. Typically, the added benefit is just increased distance, and the second move is typically a throw. The pairing of a kara-canceled move with a throw is thus known as a kara throw.
Kara Cancelling Distance Comparison
Every character in the game has a move which can be kara-canceled, but each individual move typically adds a different amount of distance. Some moves actually give no distance when kara-canceled, and a few moves actually give negative distance, meaning they move the character backward.
Below is a list of the added distance gained when kara-canceling each move, excluding karas with minimal effect (under 0.010 distance). "Lenient" karas, like the ones built into Sagat's f.LK and f.HK, are not included because they are not technically karas.
As an example, when Vega performs his Far HK kara throw, he adds 0.289 distance to his throw range (1.07), for a total of 0.289 + 1.07 = 1.36. As a reference, the stage is 15.0 units wide, and the characters start 3.0 units apart at the beginning of the round. All numbers are truncated values (rounded down).
Note that the proximity range of normals affects how and when they can be used. For example, Evil Ryu's Far HP has a good kara range at 0.2204, but his Close HP doesn't move him forward at all. Additionally, many close normals actually have shorter proximity distance than the character's throw range, which makes them pointless for kara throwing.
Moves with a blue background are special-only karas; they can be used to kara EX specials of a higher priority, supers and ultras. Moves with a red background are negative karas that move backwards a noticeable distance.
| Character | Kara Canceled Move | Distance Added |
|---|---|---|
| Abel | close LK | 0.165 |
| Abel | far LK | 0.091 |
| Abel | crouching HK | 0.174 |
| Adon | close MK | 0.306 |
| Adon | far HK | 0.098 |
| Akuma | close HP | 0.126 |
| Akuma | far HP | 0.178 |
| Akuma | close HK | 0.294 |
| Akuma | far HK | 0.041 |
| Balrog | Any Dash Punch (L/M/H) | 0.110 |
| Balrog | Any Dash Punch (EX) | 0.120 |
| Blanka | far LP | 0.218 |
| Blanka | Forward Hop | 0.221 |
| Cammy | far MK | 0.065 |
| Cammy | crouching MK | 0.031 |
| Chun-Li | forward+MK | 0.060 |
| Chun-Li | Hazanshu (H) | 0.070 |
| Chun-Li | Lightning Kicks (EX) | 0.200 |
| Cody | close HK | 0.102 |
| Cody | far HK | 0.135 |
| C. Viper | Burning Kick (H) | 0.060 |
| C. Viper | Burning Kick (EX) | 0.070 |
| Dan | Dankukyaku (L/M/H) | 0.021 |
| Decapre | close LP | 0.094 |
| Decapre | far LP | 0.012 |
| Decapre | close LK | 0.012 |
| Decapre | close MP | 0.031 |
| Decapre | far MP | 0.043 |
| Decapre | far MK | 0.064 |
| Decapre | close HP | -0.057 |
| Decapre | far HP | 0.025 |
| Decapre | crouching MK | 0.031 |
| Decapre | down forward+MK | -0.046 |
| Dee Jay | far MP | 0.018 |
| Dee Jay | close MK | 0.138 |
| Dee Jay | crouching MP | 0.021 |
| Dhalsim | crouching HK (slide) | 0.013 |
| Dudley | standing HP | 0.070 |
| Dudley | Machinegun Blow (H) | 0.442 |
| Dudley | Machinegun Blow (EX) | 0.542 |
| E. Honda | Hundred Hand Slap (H) | 0.120 |
| Elena | standing LK | 0.098 |
| Elena | crouching HP | 0.059 |
| Elena | crouching HK | 0.096 |
| Elena | forward+MP | 0.038 |
| Elena | forward+MK | 0.116 |
| Elena | down forward+HK | 0.010 |
| El Fuerte | far MK | 0.011 |
| El Fuerte | close HK | 0.016 |
| El Fuerte | far HK | -0.025 |
| Evil Ryu | far HP | 0.220 |
| Evil Ryu | close HK | 0.185 |
| Evil Ryu | far HK | 0.076 |
| Evil Ryu | crouching MK | 0.350 |
| Evil Ryu | forward+MK | 0.132 |
| Evil Ryu | Axe Kick (L) | 0.392 |
| Fei Long | far HK | 0.102 |
| Fei Long | forward+MK | 0.018 |
| Fei Long | Rekkaken (H) | 0.167 |
| Gen | (Mantis) close / far MK | 0.259 |
| Gen | (Crane) close / far MP | 0.050 |
| Gen | (Crane) crouching MP | 0.063 |
| Gouken | close MK | 0.153 |
| Gouken | far MK | 0.052 |
| Gouken | far HK | 0.191 |
| Guile | far MP | 0.186 |
| Guile | close MK | 0.255 |
| Guile | crouching HK | 0.125 |
| Guile | Flash Kick (ALL) | 0.237 |
| Guy | close MP | 0.031 |
| Guy | far MP | 0.135 |
| Guy | close HK | 0.257 |
| Guy | downforward+HK | 0.073 |
| Guy | Hozanto (EX) | 0.146 |
| Hakan | forward+HP | 0.024 |
| Hakan (not oiled) | Oil Rocket (ALL) | 0.120 |
| Hakan (oiled) | Oil Rocket (ALL) | 0.100 |
| Hugo | standing MP | 0.046 |
| Hugo | standing MK | 0.017 |
| Hugo | standing HP | 0.017 |
| Ibuki | standing MK (neutral) | 0.175 |
| Ibuki | crouching MP | 0.219 |
| Ibuki | Kasumi Gake (ALL) | 0.250 |
| Juri | close MP | 0.175 |
| Juri | far MP | 0.266 |
| Ken | forward+MK | 0.413 |
| Ken | forward+HK | 0.325 |
| Makoto | forward+LK | 0.336 |
| Makoto | forward+LK xx Karakusa (6f window, later = farther) |
0.41~0.52 |
| M. Bison | close MK | 0.025 |
| Oni | standing HK | 0.242 |
| Oni | back+MP | 0.205 |
| Poison | close LP | 0.053 |
| Poison | far MP | -0.136 |
| Poison | forward+MP | -0.030 |
| Poison | crouching MK | 0.020 |
| Rolento | close LK | 0.105 |
| Rolento | far LK | 0.257 |
| Rolento | close/far MP | 0.042 |
| Rolento | close MK | 0.217 |
| Rolento | far MK | 0.111 |
| Rose | crouching HP | 0.020 |
| Rufus | close HK | 0.050 |
| Rufus | far HK | -0.043 |
| Rufus | Galactic Tornado (L) | 0.050 |
| Rufus | Galactic Tornado (EX) | 0.071 |
| Ryu | close HK | 0.185 |
| Ryu | far HK | 0.104 |
| Sagat | close MK | 0.120 |
| Sagat | forward+LK | 0.039 |
| Sakura | close / far LK | 0.054 |
| Sakura | close HP | 0.195 |
| Sakura | far HP | -0.015 |
| Sakura | crouching HP | 0.106 |
| Sakura | forward+MK | 0.019 |
| Sakura | Shouoken (EX) | 0.100 |
| Seth | far LK | 0.088 |
| Vega | close / far HK | 0.289 |
| Yang | close / far HK | 0.104 |
| Yang | Mantis Slash (H) | 0.189 |
| Yun | close / far LK (Genei Jin) | 0.350 |
| Yun | close MP (non-Genei Jin) | 0.178 |
| Yun | far MP | 0.122 |
| Yun | close MK (non-Genei Jin) | 0.044 |
| Yun | far MK | 0.178 |
| Yun | crouching MK | 0.170 |
| Yun | crouching MK (Genei Jin) | 0.153 |
| Yun | forward+MK | 0.168 |
| Yun | Lunge Punch (L, Normal/Genei Jin) | 0.366 |
| Yun | Shoulder (L) | 0.217 |
| Yun | Shoulder (L) (Genei Jin) | 0.340 |
| Yun | Shoulder (M) | 0.169 |
| Yun | Shoulder (M) (Genei Jin) | 0.370 |
| Yun | Shoulder (EX) | 0.247 |
| Zangief | far HK | 0.221 |
| Zangief | Banishing Flat (L) | 0.130 |
