LaTeX Tip of the Day – paragraph styles
There are two really quick commands to change the way new paragraphs begin. In the preamble (before begin{document}), add:
setlength{parindent}{0.0in}
setlength{parskip}{0.1in}
and set the two lengths to suit your needs. Acceptable units are: in, cm, mm, pt, ex, em (ex and em are approximately the width of the letters x and m, and scale with the font size), or you can use setlength{parskip}{1.0baselineskip} to get a full blank line before each new paragraph (the baseline skip is the vertical distance from one line of text to the next), or replace 1.0 with some other number for bigger or smaller spacing (which also scales properly if you increase the line spacing).
If you have a paragraph with special needs, you can specify noindent right before the text. You can also insert a space equal to th paragraph indent with indent.
You can also change line spacing with
renewcommand{baselinestretch}{1.2}
where the numerical factor is 1 for single spacing, 2 for double spacing, etc.