Almost everything is copied from the UMK3 General Gameplay Guide when only some stuff was changed due the MK1 gameplay difference.
Abbreviation key for attacks and commands in all character guides:
F = Forward
B = Back
D = Down
U = Up
LP = Low Punch
LK = Low Kick
HP = High Punch
HK = High Kick
BL = Block
JK = Jump Kick
JP = Jump Punch
SHK = Standing HK
SLK = Standing LK
RH = Roundhouse
aa = Anti Air
TP = Teleport Punch
Inf = Infinite
otg = Off/on the Ground
gc = Glitch cancel
Blocking:
Blocking in MK is different from virtually every fighting game. Obviously, there is a button for block, rather than holding back, which eliminates the need for proximity blocking entirely, and you can buffer moves easily while blocking. A not so obvious concept about blocking in MK is frame update. Character sprites are behind by one tick in MK, so you can block things upon the frame they connect. There is a similar concept in SFA3 called "Blue Blocking" which your character turns blue and it takes away less guard stun meter. You can essentially Blue Block sweeps and low hitting attacks in MK by tapping D+BL on or just before the frame the sweep will connect, and your character will not have to duck, enabling them to counter faster, or sometimes duck half way, and stand back up instantly. It is a good idea to learn how to block only when absolutely needed, so you aren't stuck in standing back up frames after releasing block, rather, releasing block at the end of the contact and standing up while unblocking.
Jabs/Kara Jabs:
You can cancel a LP or HP by tapping any other attack button, canceling forward direction with LP or HP and then immidiately blocking will not allow the opponent to hit you. Still there are some moves that could be faster and could hit you like crouch kicks mostly. Kara Jabs is basicaly the same thing in MK1, Canceling a LP or HP with block.
Corner Jabs:
Once you have someone backed into the corner and blocking, tap LP, because there is no pushback for this scenario in MK1, UNLESS the opponent's character is stand up, if they are ducked you will not be pushed away. They will be in the corner, and they will eat pixel after pixel of block damage. The only thing that the victim can really do is escape with a special move (fly kick, square punch, etc), uppercut, or crouching LK. If you can sniff out when they are going to try to do any of those, do a knee or special move, preferably a containment. If they block a knee you will not be pushed back like it was in umk3, so do it wisely to keep them trapped in the corner. Try to throw out 4-6 jabs then knee, because thats usually when people realize that they are losing a lot of energy to chip damage. If the knee hits, continue to jab and keep them locked down. Also, don't forget to hold back while you do the corner jabs so that they can't counter throw. If you are under corner jab pressure, after the first 1 or 2, try and spam on crouch kick, and you have a good chance of
sneaking out.
Throw Defense:
Hold "Back" and you will not be thrown. Up+Back, Down+Back, Down+Back+Block also works. Many people complain about throws, but throw prevention is pretty easy in MK, and it's been this way from MK1 through MK4. In MK1 there is a way for throws to not be escapable if someone did it to you after you got some move (whiff backwards shadow kick, crouch kick, etc).
Crossup Throws:
This tactic is best used while an opponent is being defensive. The best way to describe this is when you are at jump distance, do an early jumpkick, so you land directly on top of the victim, without hitting them. You will land overlapping the victim's sprite. If you hit LP right as you land, you will have a very good chance of connecting a throw because they have to hold back to prevent the throw, and the direction is pretty hard to determine in such a close situation in a small amount of time.
BTW there are no crossover JKs/JPs in MK1 LOL!
Punishment/Retalation Mode:
When certain moves are blocked, they will roll up into a ball and float right next to a player setting up a punisher juggle, sometimes they float away from you but still can be punished. Other punishment scenarios to look for are against Liu Kang's Dragon Kick, Sonya's leg grab, Sub-Zero's Slide and etc. All of these, when blocked, make them stay locked in place, generally very close to you, free to be countered, but only within a very brief time. This is not much longer than the amount of time it takes you get out of blocked so you must react quickly.
Anti-Air:
Commonly referred to as "aa" directly in place of the attack which would be used as anti-air. These are attacks which are used to take someone out of the air. It is very important to understand every character's best aa opportunities. A standing HK is a very simple and effective way to anti air someone. Some characters can aaHP others out of the air very easily, setting up decent, to super high damage combos. Some characters should go for RHs on their aa's because it will set up combos, traps, or other tactics and set ups. The best simple form of aa is the uppercut. Try and scout early JKs.
Pushback:
Some attacks/special moves if are blocked or hit opp in corner, the attacker gets pushed back to just under jump distance. If you juggle someone in the corner with LP/HP jab, or a jab after just about any other hit, you will be pushed back, but you can cancel this with any special move. The same thing applies to when you throw out 3 jabs in succession and they are blocked, the third punch frame will freeze and you will be pushed back. At any time during the "iceskate", you can cancel out with a special move.
Wake Ups:
In MK and many other games, there are times when a move that is usually unsafe to do when the person has the ability to block can be used to generally make you character get up more quickly and reward you for doing so with a potential juggle, or counter after blocking when in close range. What you must understand is that of course, even though this is inherently unsafe in all fighting games due to baiting, errors, etc, it has become a huge part of fighting game psychology, so it is always a factor. "Will they bait" "Will they wake up" etc. These are sometimes referred to as 50/50s. Some characters have excellent wake up moves that are actually safe in certain situations. Moves that will mostly be used as a "Wake Up" are Shadow Kick, Slide, Teleport Punch, etc. Check the
Character Guides for some wake up scenarios.
Glitch Canceling:
Explained in Sub-Zero's Guide since he is the only one that has real glitch cancel in MK1.
The Throw/Uppercut "Brokeness":
This will be hard to explain but i will give a try. In a two player game (and only two player) game if you interupt a move/special move or any attack of your opponent with a throw and you do a special move/fireball (the special move should not be anti air) immidiately after the throw without loosing any frames, it will be unblockable. There is no 100% sure way to
always get this but you will figure it out by yourself when you can do it and when not.
That can often lead you into a victory or into a trouble - for example Raiden - Throw, Torpedo is punishable, because if the Torpedo is not aa the opp can punish you even if it hits. And if you do that vs Scorpion you risk more than half of your energy in this scenario.
Still its a very useless stuff in corner and mid-screen in some scenarios. You can get even uppercut after the throw and it wont be unblockable.
Another "Broken" move which can lead into unblockable attacks is the uppercut. So far only Raiden has real advantage of this because of his pseudo infinite. Canceling attack with uppercut, then teleport with no frame lost and uppercut again. I know in some very very rare cases Cage can get uppercut unblockable SK or Sweep after it but thats it.
Some other moves that can lead into unblockable stuff are the freeze and leg grab.
Dont forget that if your opponent just ducks the unblockable uppercut/move will whiff (if its not the torpedo because it hits opps ducked).
Its COMPLETELY possible i miss some stuff, i will check it again soon and see if i can add some stuff more.
8) 
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