Pronunciations

Below you'll find correct pronunciations for many of the commonly mispronounced Harry Potter characters, creatures and terms. 

Characters
Albus Dumbledore [ Al-bus Dum-bell-door]
Alastor [ A-LAS-tor ]
Bellatrix Lestrange [ BELL-a-trix La-STRAWNGE ]
Cedric Diggory [ SED-ric DIG-ory ]
Dedalus Diggle [ DEE-da-less DIG-gull ]
Draco Malfoy [ Dray-co MAL-foy ]
Firenze [ Feer-EN-zee ]
Ginny Weasley [ jin-ee Weasley ]
Hermione Granger [ Her-my-oh-knee Grain-jer ]
Kreacher [ CREE-chur ]
Lucius Malfoy [ Loo-SEE-us Malfoy ] This is the correct way, it is not LOO-shas as its commonly referred as. 
Ludo Bagman [ Lew-do Bagman ]
Minervera McGonagall [ Min-erv-era M-gon-a-gall ]
Mundungus Fletcher [ Munn-DUNG-gus FLET-chur ]
Nagini [ nag-EEN-ee ]
Narcissa Malfoy [ nar-SISS-a Mal-foy ]
Professor Trelawney [ Tre-lawn-ee ]
Rabastan Lestrange [ Ra-BASS-ton La-STRAWNGE ]
Rodolphus Lestrange [Ra-DOLL-fuss La-STRAWNGE ]
Rowling [ Roll-ing ]
Rubeus Hagrid [ Roo-be-us Hagrid ]
Seamus [ SHAME-us ] 
Sirius [ Serious ]
Voldemort [ Vole-de-more ]

Terms
Accio [ AH-see-oh ]
Animagi [ An-i-MAYJ-i ]
Beauxbatons [ Bo-Bat-ons ]
Circe [ SIR-see ] Colloportus [ Cull-low-POR-tus ]
Diagon Alley [ Die-a-gon Alley ]
Eeylops [ EYE-lops ]
Erised [ ERR-i-sed ]
Fidelius Charm [ Fi-DAY-lee-ous Charm ]
Flagrate [ Fla-GRA-tay]
Grimmauld Place [ GRIM-mold Place ]
Gryffindor [ Griff-in-door ]
Hogsmeade [ Hogs - Meed ]
Hufflepuff [ Huffle-Puff ]
Knuts [ ca-noots ]
Imperturbable Charm [ Im-per-TER-bub-bull Charm ]
Legilimency [ La-JILL-a-men-see ]
Occlumency [ AW-clue-men-see ]
Ollivanders [ Oll-iv-anders ]
Patronus [ Pa-TRONE-us ]
Pensieve [ Pen-siv ]
Quidditch [ Quid-itch]
Ravenclaw [ Ray-ven-cawl ]
Slytherin [ Slyth-erin ]
Tarantallegra [ Ta-RON-ta-LEG-gra ]
Triwizard Tournament [ Tri-Wizard-tor-na-ment ]
Veritaserum [ VER-rhett-a-SEE-rum ]
Wizengamot [ We-zen-gaa-mought ]

Creatures
Basilisk [ Bas-a-lisk ]
Boggart [ Boh-gart ]
Kneazle [ Knee-zel ]
Phoenix [ Fee-nix ]
Thestrals [ THESS-strulls ]
Veela [ VEE-la ]