An acronym is usually written in uppercase. Examples: AWOL, LOL
Acronyms with four letters or more and are pronounceable, we may use upper- and lowercase. Examples: Aids, Nasa, Interpol
Contemporary acronyms do not need full stops. Examples: NATO, Scuba
The contemporary rule is to write the full name out when first mentioned (with the acronym in brackets). Use only the acronym after this. Example: ‘The North Atlantic Treaty Organisation (NATO) will decide on the issue. NATO leadership is made up of…’
Some acronyms are so familiar we can assume readers recognise them. We do not need to write them out. Examples: Aids, Unicef. Many acronyms have become standard words. Examples: radar (radio detection and ranging), scuba (self-contained underwater breathing apparatus), and laser (light amplification by the stimulated emission of radiation).
Use ‘an’ in the place of ‘a’ when the article precedes a vowel sound. It’s ‘an honour’, where the 'h' is silent, but ‘a Unicef’ issue if it is pronounced ‘yoo’. It’s the sound that matters.
The word ‘the’ is unnecessary before some acronyms are pronounced as words, i.e. Interpol, NATO, Radar.