When using "etc." in parentheses, use it as you would in a regular sentence: I like healthy foods such as fruits, vegetables, cereals, and so on. For example: She wrote a letter to her friend etc. (period).
When an entire sentence is parenthetical, use full stops inside brackets as a general rule. In all other circumstances, place full stops outside the closing brackets. This is true whether you're using HTML or plain text.
The abbreviation should be surrounded by parenthesis. Otherwise, it is interpreted as a language label or an acronym.
A pair of em dashes can be used instead of parentheses. Dashes are less formal than parentheses, but they are also more noticeable. Use dashes to attract emphasis to the parenthetical information. Use parenthesis to insert the parenthetical material more quietly.
Using dashes instead of parentheses is a common writing technique in journalism. A story told through interspersed quotes or anecdotes often uses this method of insertion. The reporter will often follow this with a parenthetical note explaining the reason for using dashes instead of parentheses.
For example, if I wanted to tell you that John said Mary was the best friend he had ever had, I could either write it out like this: "John said Mary was the best friend he had ever had." Or I could write it as one sentence by using dashes instead of parentheses: "John--who had just gotten off of work--told Mary that she was the best friend he had ever had." In this case, the explanation I give after the fact is that dashes were used because it's an anecdote within a quote. But this is not always the case; sometimes reporters use dashes instead of parentheses for no apparent reason at all.
The important thing is that you become familiar with how to use dashes in place of parentheses.
Brackets: How to Punctuate Them
Rule 1: Use parenthesis to contain material that explains or serves as a digression. He finally responded (after a five-minute pause) that he didn't comprehend the query. If the content in parenthesis comes at the conclusion of a sentence, the period comes after the parentheses. Otherwise, the comma is used instead.
To contain material that explains or serves as an aside, use parenthesis. He gave me a nice $500 bonus. I received $10,000 in bonuses this year.
The and (curly bracket) and [or] (square bracket) keys are shared on US keyboards. Hold down the Shift key while hitting the or key to make the curly bracket. Holding down the Shift key while hitting the and key will produce a square bracket.