The control's pretty simple.
Square for weak attacks
There are 3 different combos for most chars (note the # of squares/hits depends on the character)
Combo#1: Back (or Forward) + Square, Square, Square
Combo#2: Down + Square, Square, Square
Combo#3: Square, Square, Square
Triangle for strong attack
As with the square attacks, the # of triangles/hits depends on the character and some may not have all 3
Grab/Grapple: Forward + Triangle
Combo#1: Back + Triangle, Triangle, Triangle
Combo#2: Down + Triangle, Triangle, Triangle
Combo#3: Triangle, Triangle, Triangle
X for support attack/counter
Uses 2 portions of special gauge
Pressing X normally does the support attack
Pressing X while being attacked/combo'd by opponent will perform a counter
Decade only:
Press X to use the Final Form Ride you set for this button (uses 1 portion of the special gauge)
Press X when being attacked to use the counter Final Form Ride you set for this button (I'm not sure whether it uses 1 or 2)
O for normal special attacks
Up to 4 different variation depending on characters
Variation#1: O (hold down O to charge for some characters, mash O for more hits on some, just O for others)
Variation#2: Back (or Forward) + O (the same as above... hold, mash or not depends on characters)
Variation#3: Jump (Up) + O
Variation#4: Down + O (Decade only IIRC. Uses one of the Final Form Ride you set)
Decade only:
V#1: Use Final Form Ride set for O
V#2: Use Final Form Ride set for Back (or Forward) + O
V#4: Use Final Form Ride set for Down + O
Final Form Rides take 1 portion special gauge
L1: Evade roll left
R1: Evade roll right
L2: Form change (at full special gauge)
R2: Ore no hissatsu waza, rider version! (aka Finisher, usable only with full special gauge)
Hold down: Charge special gauge
Other notes:
Tap forward twice (and hold) while not attacking to run (+ triangle to perform a sliding attack)
Tap forward twice while in the middle of your attacks to 'cancel' out of it (uses 1 portion special gauge)
Decade Final Form Ride (or ridebooker) Setup Menu
O : Choose a final form ride (or ridebooker sword or gun) for O
Back/Forward + O: Choose a final form ride (or ridebooker sword or gun) for Back/Forward + O
Down + O : Choose final form ride (or ridebooker sword or gun) for Down + O
Support: Choose final form ride (or ridebooker sword or gun) for support button (square)
Counter: Choose final form ride (or ridebooker sword or gun) for counter (square when being attacked)
... such a long post. I have too much time, lol. Also... this is what one does when one's bored: