\setcounter{tocdepth}{n} where n is an integer, tells latex how deep to make TOC. n
depends on the class type, see above.
\setcounter{secnumdepth}{m} tells latex which entries in the TOC (which depends on
the first command above) to give it a number to the left side. default is 3 I think. But
better to have numbers for all sections and subsection in TOC.
Do the above in preamble of document.
some links on TOC in latex
can change depth of toc using \setcounter{tocdepth}{depth} in preamble. it looks like
default depth is 3.