Bosses are patterns
Every boss repeats a small set of attacks in a readable order. Watch the first cycle and you already know most of the fight.
Dodge through the attack, then punish. Trading hits with a boss is a losing trade almost every time.
Watch the health bar
A boss changes behaviour as its health drops. The move that opened the fight may not be the one that ends it.
Learn the phase changes so a surprise swing does not catch you.
Keep one reliable tool
Bring a weapon that works with no setup. Combos that need a full rotation rarely survive a boss.
A shield helps on fights where a parry turns a heavy hit into an opening.
Save your flask
Enter a boss at full flask if you can. Healing taken early is healing missing when the boss is low.
Next: Parry and timing and Boss Cell progression.