Space (a)   time (s) after the comma.

Space (a)   times (s) after the semicolon.

Space (a)   time (s) after the question mark at the end of a sentence

Space (a)   time (s) after the colon within a sentence

Space (a)   time (s) before and after the ampersand.

Space (a)   time (s) before and after the @ sign when used within an email address.

Space (a)   time (s) between the dollar sign and the number e.g. $3

3# means (a)   in keyboarding.

#3 means (a)   in keyboarding.