Paragraphing is essential if you want your post to be easily read. I have seen posts which are perfectly literate but all squashed up into one, gigantic paragraph. It is such a strain for other people’s eyes!

Basically, a new paragraph is started when you start to change the subject or when someone starts speaking. If you can, after you have typed up a post with paragraphs, try to fit a little sub-title for each paragraph. If you can do that, then the paragraph should be ok.

When separating speech from the main text, use a new paragraph. Otherwise, it will be muddled up and people cannot tell what action is and what speech is.
Spacing is ever so important. You can’t just string words together like this:
Thelittleboywasverysmallandshort.
It’s ever so hard to read! Between each word, there should be a space:
The little boy was very small and short.
Also, after a piece of punctuation, there must be a space before you start the next bit of typing.