Which apostrophe character should I use

Many languages use an apostrophe-like character.

The problem this presents is that the traditional apostrophe (like what we use in English) is a punctuation character. It works okay for saying something's "elided" (like in something's), but it's not appropriate to represent a segment (like glottal stop in Tongan), super-segment (like aspiration in Nivkh or ejective status in Navajo), or modifier (like in Uzbek). There are special characters for this.

Here are some common apostrophe-like characters:

symbol	name	codepoint	use for what
'	apostrophe	U0027	misc
`	backtick	U0060
ʻ	turned comma / ʻokina	U02BB	glottal stop (in Polynesian languages) also used for Uzbek oʻ, gʻ, etc.
ʼ		U02BC	glottal stops, aspiration, etc.
‘		U2018	start quote
’		U2019	end quote