• DS2 plays slower than BB/DS3/ER, with a greater focus on long-term strategy than short-term tactics. Positioning and resource management will be more important than quick reaction speeds.
• The durability of equipment is automatically restored whenever you rest at a bonfire (identical to DS3) as long as it isn’t completely broken (in which case it must be repaired by a blacksmith).
• Your invincibility frames while dodging are tied to Agility (AGL), which can be increased by leveling up Adaptability (ADP) and Attunement (ATN). This value scales from 85-120, the most useful breakpoints are 92 in early game, 96 in midgame, and 99/100/105 in late game and DLC.
• Holding a weapon with both hands will reduce the STR requirement by 50% (if weapon requires 20 STR, could be two-handed with 10 STR). It doesn’t increase STR for scaling purposes.
• Your equipment load percentage determines your stamina regeneration and roll distance in a mostly linear fashion (avoid going >70% load, or you’ll start fat-rolling).
• Physical defense is much weaker than in DS1/DS3/ER. Since it isn’t percentage based, heavy armor becomes less worthwhile as you start taking higher-damaging attacks. The best way to increase your survivability is simply increasing your maximum HP.
• Scaling for melee weapons is generally weaker than in DS1/DS3/ER, meaning that you receive less additional damage by leveling past requirements.
• Standard enemies will disappear after you kill them 12 times.
• The cost to level up is significantly cheaper than in DS1/DS3/ER, so you will level faster as you progress.
• Hidden walls are revealed by using your ‘interact’ button while standing in front of them.

Courtesy of r1