Material spell components are consumed/destroyed/expended when the spell is cast, unless specifically noted otherwise (PHB p. 113-114)
Priest holy symbols are not lost when a spell is cast (PHB p. 114)
Casting from Scrolls
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Spell Books & Learning new spellsSpell Books
A spell requires its level plus 0–5 (1d6-1) additional pages (DMG p. 63)
One spell book page cost 50 GP (DMG p. 63)
Maximum spell book sizes: Standard 100 pages; Traveling 50 pages; Scrolls 25 pages (DMG p. 63)
A wizard can never have a spell in his book that he does not know (PHB p. 107)
Learning new spells
Wizard scrolls require a read magic spell to decipher (PHB p. 144)
A wizard cannot learn a spell that is higher level than he can cast (PHB p. 107)
A check is made to see if a spell can be learned. If it fails, another check can be made after the wizard advances to the next level (provided the wizard still has access to the spell) (PHB p. 22)
Both versions of a reversible spell is recorded in the wizard's spell book (PHB p. 168)
Standard time required to add a spell to a spell book: one to two days per spell level of spell being entered (DMG p. 62)
Learning from Scrolls (Scroll Research)
The time and cost required is halved (DMG p. 61)
Scroll Research can never be done in an adventuring situation. The wizard must have carefully controlled conditions to even attempt it. (DMG p. 61)
Regardless of success or failure of the research, the scroll is destroyed. (DMG p. 61)
Scribing ScrollsWizards
Gain the potential to scribe scrolls at 9th level (PHB p. 43 / DMG p. 117)
Must have their spell book at hand to guide their work (DMG p. 119)
Priests
Gain the potential to scribe scrolls at 7th level (DMG p. 117)
Must work on a specially prepared altar (DMG p. 119)
The spellcaster knows the basics of the art and has learned where to look for the information he needs to make the attempt. The exact process for each spell is still a mystery to him. He may consult a sage, seek the guidance of a higher level spellcaster, or even use spells to call upon greater powers. (DMG p.117-119)
Brewing PotionsWizards
Gain the potential to brew potions at 9th level (PHB p. 43 / DMG p. 117)
Potions are primarily the province of wizards, although healing and curing potions are beyond the ken of wizards (DMG p. 119)
Require a complete alchemical laboratory (DMG p. 120)
Priests
Gain the potential to brew potions at 9th level (DMG p. 117)
Can prepare potions related to healing and cures (DMG p. 119)
Require an altar specially consecrated to the purpose of brewing potions (DMG p. 120)
Druids
Druids who spends 3 slots in the Herbalism nonweapon proficiency can create magical herbal brews (The Complete Druid's Handbook p. 103)
Fabricating other Magical itemsWizards
Gain the potential to create other magical items at 11th level, if he has the spells (DMG p. 117)
Priests
Gain the potential to create other magical items at 11th level (DMG p. 117)