Adding double quotes is risky with regard to "`", "$" and other special shell characters.

Adding single quotes is safer, but will fail if the argument itself contains single quotes.

To my knowledge, the correct shell escaping is to surround your argument with single quotes, and before doing that, replace each contained single quote

  '

with the following sequence (1):

  '\''

Alternatively, you can use (2):

  '"'"'

Both sequences work the same way: First, terminate the single-quoted string. Then, add an escaped single quote, either with backslash (1) or by encapsulating into double quotes (2). Finally, start an new single-quoted string.