\linespread work?\linespread{factor} is supposed to multiply
the current \baselineskip by <factor>; but, to all
appearances, it doesn’t.
In fact, the command is equivalent to
\renewcommand{\baselinestretch}{factor}: written that
way, it somehow feels less surprising that the effect isn’t immediate.
The \baselinestretch factor is only used when a font is selected;
a mere change of \baselinestretch doesn’t change the font, any
more than does the command
\fontsize{size}{baselineskip} — you have to follow
either command with \selectfont. So:
\fontsize{10}{12}%
\selectfont
or:
\linespread{1.2}%
\selectfont
Of course, a package such as setspace, whose job is to
manage the baseline, will deal with all this stuff — see
“managing double-spaced documents”. If
you want to avoid setspace, beware the behaviour of
linespread changes within a paragraph: read
“\baselineskip is a paragraph parameter”.
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=linespread