2A is your fastest normal, and lowprofiles a lot of stuff. It’s got decent range and hits low, so it’s your main go-to when you’re up close.
j.A is really really good. Throwing it out can snuff a lot of Chie and Yosuke approaches a lot of the time.
Never throw more than 1 fan (5B) against a crouching opponent. The second fan will whiff crouching and leave you open.
Practice airdash-back-fan. No, seriously. If you can’t do run-airdashback-fan consistently, it takes away a lot from your game. Fans are important. They can hit low. That said:
Don’t spam too many fans. j.B gives you really bad recovery on landing, so a lot of characters can just use moves that eat the fan and hit Yuki on the way down.
Another way to throw quick fullscreen fans that hit low is to shorthop (2A+C, and do a 6B at the apex of the hop).
5AA, 236A (instant release) is a blockstring. Most everything else is not a true blockstring and you can get DP’d out of stuff if you aren’t careful.
For a lot of matchups, j.D is your friend. You can use it after fan throws to apply more pressure and cover ground as you land. You can also use it to slow your decent and avoid high-pressure situations where you might get airgrabbed or hit by stuff on the way down (Yosuke 2B comes to mind here).
Try to confirm off of 5AA. 5A and 5AA are both jump cancellable, so are mostly non-commital. 1/2/3B is also jump cancellable, but will whiff on opponents if you’re too far away. After 5A or 5AA, you can jump cancel into a bunch of stuff (airbackdash fan ; superjump j.1B, j.D, backdash fan ; jumpback, airturn dash ‘backward’ j.A).
If you’re going for an unblockable Maragi setup, try to finish your first combo with a sweep to force the knockdown. Otherwise they can easily tech and avoid.
If your unblockable Maragis keep gettin late-teched, start using SB Agi instead so you can pressure a tech with the first explosion and then detonate the second Agi explosion.
You can still roll while you have B held down for B Agi/SB Agi. You can use this to create left/right mixups, especially if you use SB Agi and detonate the A as you run towards your opponent.
Don’t forget to throw. Yukiko is very good at snagging counterhits with 5A and fans, so it’s easy to forget to mix it up.
Yuki’s AoA is one of the ‘safer’ ones if done from max range. It’s very slow to come out, though, so don’t do it often against someone that can react easily to it.
Cover your 4/5/6Ds with 5/6B fan throws. At max range, 6D, 6B will often catch opponents trying to counterhit the 6D and let you get a free full-screen combo.
C Maragi is slow to come out, and detonating it with C is often not desirable due to the recovery on C moves. Instead, detonate with C+D (throw whiff) which recovers faster, or 214C (Fire Boost) to build free stocks.
Turn on Fire Break more often. Most people just like to save this for unblockable setups that lead to Maragi loops. Turning it on when you have 50 meter or more guarantees damage outside of getting Dead Angled/Bursted as long as you touch your opponent (5AA, 236A, 236236C/D is a true blockstring unblockable). It also tends to get your opponent worried about running into a D Maragi or random fire traps.
That said, having Firebreak up also gives you an unblockable Maragi loop combo if you have at least 25 Meter (and still will do some damage if you don’t). 5AA, 236A One-More-Burst is an unblockable setup with Fire Break that leads you into whatever combo you want.
Yukiko’s IK is one of the better ones to punish telegraphed supers, and is even a viable wakeup option sometimes due to the startup animation being ‘masked’ in what looks like a regular crouch. Just throwing it out there.
Jump, air-turn, C makes Yuki’s persona extend much further than just doing j.C. This allows you to pressure some opponents more effectively and stuff their approaches (Akihiko is particularly vulnerable to this).
Don’t be afraid to Dead Angle (Counter Assault) stuff. Yuki’s normals aren’t exceptional for getting her out of a pickle, so DA is one of the better options she has to get opponents off of her.
When your Persona is broken, try to end combos with a sweep (2A+B), which is jump-cancellable. Jump after the sweep and do a j.1B. Depending on the opponent’s rise, the fan may create a (somewhat) ambiguous setup where the opponent may try to anticipate blocking your jump attack high, and get hit low by the fan.
Anti-airing with 1/2/3B can lead to 236D on Counterhit, which sets you up for big combos. Not advisable against chars with dominant jumpins, though, like Labrys/Slab.
When close to the corner, you can Dia opponents (B+D) and cause a wallbounce that allows for combo followups if you hit an airborne opponent high enough.
Agidyne D does more damage than C, but C allows for easier oki. Your call.
Watch for rolls on your opponent’s part. Rolls can get a lot of characters out of Yuki’s pressure, and with Yuki’s slow/limited normals, they can be hard to punish if you aren’t watching carefully. This is especially true because only 2A and 2AA can be gatling’d to 5A. 2AAA can only be cancelled into sweep (2A+B), which is a fairly minimal punish. You can also try throwing, but Yuki’s throw range is a bit smaller and slower than a lot of the cast.
[*]Don’t forget to detonate Agi in combos that could kill. It becomes habit to hold the Agi for oki, but if it’ll kill … then do it!
Buncha other stuff that I can’t think of right now.