documentclass{article}
usepackage{lipsum}
usepackage{titlesec}
itlespacingsection{0pt}{12pt plus 4pt minus 2pt}{0pt plus 2pt minus 2pt}
itlespacingsubsection{0pt}{12pt plus 4pt minus 2pt}{0pt plus 2pt minus 2pt}
itlespacingsubsubsection{0pt}{12pt plus 4pt minus 2pt}{0pt plus 2pt minus 2pt}
egin{document}
section{Section}
lipsum[1]
end{document}