The 2024 rules a DM looks up most
A DM screen holds the rules the table checks mid-fight. The 2024 rules (SRD 5.2.1) have 15 conditions, from Blinded to Unconscious. Exhaustion now stacks simply: each level gives a -2 penalty to every d20 Test and cuts Speed by 5 feet, a creature dies at level 6, and finishing a Long Rest removes one level.
Cover adds +2 to AC and Dexterity saves at half, +5 at three-quarters, and total cover means a target can't be targeted directly. Typical Difficulty Classes run Very Easy 5, Easy 10, Medium 15, Hard 20, Very Hard 25 and Nearly Impossible 30. Concentration breaks on a failed Constitution save after damage; the DC is 10 or half the damage, whichever is higher, up to DC 30.
Screenwise puts all of this on your phone: search a word, tap a card for the full rule, and pin the ones you need tonight.