Devil May Cry
Combos
These combos are based off of the basic attack mode without holding R1. These will help you get a better combo rating, especially if you do the first and follow with the second. Make sure not to hold R1 button or you will do the Air Hike or the Stinger.
Three basic slashes plus a downward strike, then an upward strike that knocks your enemy into the air like the Air Hike: Press Triangle(3), Towards + Triangle, Triangle(2).
Three basic slashes then three additional horizontal strikes. Press Triangle(3), Away + Triangle, Triangle(3).
Equip any sword and the shotgun. Holding R1 and do the following:
Dante will do a normal slash, then a cartwheel move while firing the shotgun. Press Triangle, Square.
Dante will do two slashes and pass the shotgun under his two arms and across his back, firing the shotgun twice. Press Triangle(2), Square.
Dante will do three slashes and then go into one knee firing the shotgun. Press Triangle(3), Square.
Slow Motion Amulet piece
There is a Slow Motion Amulet piece in the level after the Phantom (the level arena with eye in the center). Toward the outside is a sack or web cocoon on the ground. Break it open. Apply the Amulet and use Devil Trigger to see all your sword combos in slow motion.
Easier combos
Use sword combos as much as possible. If an enemy is too far away for you to instantaneously attack them, use your arsenal/guns until you get close enough to use your sword(s) on them to keep the combo rating lit.
Trish's moves
Trish has two moves that Dante does not. One is throwing Sparta, which is done by holding Triangle briefly and releasing. Trish will throw Sparta. You can shoot at the same targets that Sparta is attacking and do twice the damage. For the other move, fly using the Aerialheart and hold Square. Trish should fire beams of yellow light which do an amazing amount of damage. The longer you hold Square, the more beams she will shoot at once (five beams maximum).
Double shotgun blast
Stand just near the edge of a building and shoot your gun. While shooting, go to move off the edge. The moment that you are off the edge, you will immediately fire another shot from your shotgun.
Dante's Ultimate Devil Trigger attack
To do the Ultimate Devil Trigger into Sparda demon form, press L1 when Dante's life bar is low. The Sparda form is incredibly strong and deals huge damage.
Lucia's Ultimate Devil Trigger attack
When in Lucia's Devil Trigger, equip the Aerial Heart and fly in the air after they are near you. Press Triangle + Square constantly until you do not have control of Lucia. She will perform an attack similar to the Phantom's Volcano Ass attack. It will take a lot of Devil Trigger. If you keep pressing it fast it will not waste Devil Trigger at all, but it will eventually stop.