Use all capitals and no periods to abbreviate names and titles when the abbreviations are pronounced letter by letter.
Examples: NFL NEA AFL-CIO CBS IRS IRA TV
Use all capitals and no periods for acronyms. Acronyms are abbreviations which have been made into pronounced words.
Examples: OPEC NAFTA NATO BASIC SCUBA
Using abbreviations such as these is fine in standard writing, but it is a good idea to identify the acronym or abbreviation for your audience the first time word by word so that there is no misunderstanding.
Example:He got into trouble because of his involvement in an Individual Retirement Account at work. His IRA went over the limit, and he owed some back taxes.
(Spelling the name out the first time helps just in case, for example, someone were thinking of the Irish Republican Army!)