Standing Light Punch, as well as Standing Light Kick, is exceptionally fast and useful in blockstrings.
Standing Medium Punch is a very good poke for Yun because it comes out fairly fast and has good range. In addition, this Punch moves Yun forward just a bit and has a huge hitbox. What makes this move more dangerous is that if you hit your opponent you can go straight into one of his Target Combos for great damage and possibly a knockdown. You can also buffer the Shoulder Special Move while throwing this out. If you hit, you cancel right into Shoulder for damage and a knockdown.
Standing Light Kick is exceptionally fast and can be buffered into Light Punch Lunge Punch, which on hit will get you more damage and a knockdown! It can be used for blockstrings as well.
Standing Medium Kick is also a very good poke for Yun because it is fairly fast, has good reach, and has a nice hitbox. Because of these factors it's also a decent anti-air. If you hit with a Close Standing Medium Kick it floats your opponent. You can Jump Cancel out of this move on hit to do a follow-up attack or on block to make it safe. It's an excellent normal.
Standing Heavy Kick is a great poke for Yun because the hitbox is very big and the range is good. Don't do it too far out, however, as it has slow recovery. If you hit your opponent you get a techable knockdown. Not only that, but this move throws an opponent back pretty far before the knockdown, and moving your opponent toward the corner makes this move even better. This move is at its best when you have your opponent in the corner. If you hit the opponent when they try to throw out a normal (Counter Hit) you can follow this up with a Lunge Punch or even an Ultra!
RAIGEKISHUU (DIVE KICK) **AIR ONLY**
The Heavy Kick version is best for getting in on an opponent. Try to aim for the lower portion of the character. If you hit with the Dive Kick somewhere in the leg area, you usually end up with a lot of frame advantage and it is easy to follow up with a combo. If you hit higher up on the body it becomes more difficult to combo. Also, if your opponent manages to block, you should still have enough advantage to go for a command grab (Flip Grab). Again, if you hit with the Dive Kick higher up on the body you will not get as much frame advantage and your opponent may be able to react. If you accidentally hit too high with the Dive Kick and your opponent blocks you should use the EX version of the Flip Grab because it starts up a bit faster.
When using Dive Kicks it is best to not be too predictable, as you can be countered and punished if you do so. Vary the type of Dive Kick used and the heights you initiate it. Every once in a while, jump like you normally would for a Dive Kick but instead throw out a Light Kick or Medium Kick. Dive Kicks are most effective when you can keep your opponent guessing, making them much harder to react to.