Space between paragraphs is an alternative to a first-line indent for signaling the start of a new paragraph.
The worst way to put space between paragraphs is to insert an extra carriage return.
As with first-line indents, you want the space to be large enough to be easily noticed, but not so large that the paragraphs seem disconnected. Four to ten points of space will usually suffice. The larger the point size, the more space you’ll need between paragraphs to make a visible difference.

Is there any rhyme or reason when it comes to Word’s spacing “math”? I’m trying to adjust paragraph spacing in order to make certain spacing uniform. For example, my body text is 13-pt. (not my choice) Equity and line spacing is 26 pts. My block quote style is 13-pt. Equity and line spacing is 16 pts. If I have a block quotation with body text above and below it, I would prefer to have the vertical space between each paragraph mirror the spacing in the body text.
(In other words, I’d like the amount of white space between the lines internal to the body text to be the same as the amount of white space between the body text paragraph and block quote paragraph.)
This would seem to be simple — the block quote is set at 16-pt. spacing, so adding an additional 10 pts. of leading would seem to solve the problem. But that is much too large. Instead, adding 8 pts. seems about right, but I can tell it’s not quite perfect. Since it seems as f this should be a simple math problem, is this just a further instance where Word’s spacing math makes no sense?