Hand in all Bell Bearings to Twin Maidens

Collect as many final Upgrade Materials as possible

Farm Runes to buy out the Merchants' shops

Find and turn in all Scrolls and Prayerbooks to a trainer to purchase their Spells

Slay dragons to obtain Dragon Hearts (23) and buy their Incantations at the Cathedral of Dragon Communion (only 20 are required to purchase all Dragon-based Incantations)

Obtain all Larval Tears (18) for future Rebirth

Turn in all Deathroots (9) to the Gurranq Beast Clergyman

Trade for any Remembrance Weapons you may wish to dual-wield in the future

Obtain any weapons you will want to dual-wield in the next playthrough

Use Walking Mausoleums (7) to duplicate Remembrances

Collect all non-renewable Crafting Materials

Farm any Weapons or Armor that drop from Enemies that you might want (optionally respec for Arcane to increase item discovery)

If you plan on playing with a different build on NG+, pick up any equipment for your new build

If you plan on playing with a different build on NG+, respec your character by talking to Rennala

Before NG+