Simply specify either top-margin, bottom-margin, or both on your p. Where there is no specification in the CSS, the browser default will apply, so you'll need to specify these margins if you want to change them.
Originally Posted by joon
It will mean a bit of trial and error to get the exact look you want.
I recommend making sure your text size is set in a relative unit (e.g. em) and then using this unit for your margins as well, so that when the text is re-sized the space between paragraphs will remain relative to the text size.
For e.g., your style sheet might say:
Just play with it till it looks right to you. :-)
If you want to change the line height within the paragraph, set the line-height under p as well. Again, tweak it till it looks right in proportion to the paragraph spacing and text size. I find 1.3em-1.4em works well but diff'rent strokes...