Your choice is to either use block paragraphing or indented paragraphing.
The style that many writers recognise is indented paragraphing. Indented paragraphing is what you see in most published articles, short stories and novels. This is where (generally with the exception of the first paragraph of the piece) the first line of each new paragraph is indented. The first word of the paragraph appears a few spaces to the right of the rest of the paragraph. So, to create your new paragraph, press the RETURN key on your keyboard once, then press the TAB key once. (Don't press the space bar several times to create your indent.)
Block paragraphing is what you see here in this posting. Instead of the first line of each paragraph being indented, an extra blank line appears between each paragraph. This is achieved by pressing the RETURN/ENTER key of your keyboard twice. Pressing it once, drops your cursor to the next line, pressing it the second time means your text now appears under that blank line.
So, why have two styles, especially when most published text uses the indented paragraph system? Here's the science bit ...
Publishers tend to use one of two computer software packages for designing the layout of their publications: QuarkXpress (from Quark) and InDesign (from Adobe). There are other software packages out there, but these are the two biggest. When you sell a piece of your writing, the publisher will import your text into their design package. A publisher explained to me that one of these programmes doesn't recognise an indented tab from some word processor packages, whereas it does recognise the block paragraphing and (ironically) converts the blocked paragraphing into indented paragraphing!
Personally, I prefer indented paragraphing. Whilst block paragraphing works well for non-fiction, I don't think it looks right in fiction, especially if your fiction contains a lot of dialogue. Indented paragraphing works well for fiction and non-fiction.
So, to sum up with paragraphing, use either block paragraphing or indented paragraphing, but not both. And when you're writing, use the RETURN + TAB key (indented paragraphs), or the RETURN + RETURN key (block paragraph) combination.
Next week, I'll look at double-spacing and why every writer is told to use it, how to use it properly, and when you don't have to use it.