{tilde} is for questions about handling the special tilde character.
The tilde ~ character is a special, active character which stands for an unbreakable space, i.e. the line will not be broken at this space.
To typeset the tilde as character use \textasciitilde or \~{}.
The textcomp package provides a lower tilde as \texttildelow.
To write a tilde to an auxiliary file use \string~.