A proper apostrophe should look more or less like a superscript comma. See Quotes and Accents and Smart Quotes for Smart People for how to get them right.
See also straight quotes ("), rotated/flipped apostrophe (‘), apostrophe (’).
Contributed by Quentin Schmerber
Contributed by Best Studio
Contributed by Lewis McGuffie
Contributed by Peiran Tan
Contributed by Otro Bureau
Contributed by Alex Slobzheninov
Contributed by Robyn Mays
Contributed by Eliott Grunewald
Contributed by Tom Watkins
Contributed by Mario Julian Gutierrez
Contributed by Florian Hardwig
Contributed by Gareth Hague
Contributed by Aidan Molloy
Contributed by Leticia Ortín
Contributed by 205TF
Contributed by Jan Maack
Contributed by Love Lagerkvist
Contributed by Connor Davenport
Contributed by nils poppe
Contributed by Patch Hofweber
Contributed by Manish S.
Contributed by Patrick Concannon
Contributed by Irene Camera
Contributed by intornodesign
Contributed by Matthijs Sluiter
Contributed by Studio Miles
Contributed by Ganplank
Contributed by Nouvelle Noire
Contributed by Stephen Coles
Contributed by André Mora
Contributed by Swiss Typefaces
Contributed by Garrison Martin
Contributed by Emtype Foundry
Contributed by Ciarán
Contributed by FIRM.GS
Contributed by HAL Typefaces
Contributed by Nick Sherman
Contributed by Ryan Fernandez
Contributed by Kevin Scott
Contributed by Reinaldo Camejo
Contributed by Studio Six
Contributed by Feliciano Type
Contributed by Irina Carbone
Contributed by Chiara Dal Maso
Contributed by Playtype Foundry
Contributed by balsamstudio