I've been looking for a while now, for something I think is very basic. How can I use, for instance, "v0" with the 0 smaller next to the v.
Like this:

I can't find it, mainly because I'm not sure what to call it.
I've been looking for a while now, for something I think is very basic. How can I use, for instance, "v0" with the 0 smaller next to the v.
Like this:

I can't find it, mainly because I'm not sure what to call it.
If you're thinking of typesetting material in subscript position, you can do so as follows, in TeX's math mode:
$v_{0}$
Conversely, to typeset material in superscript position, you can do so (again in TeX's math mode) as follows:
$a^{2}+b^{2}=c^{2}$
To familiarize yourself some more with LaTeX and, in particular, its ways of handling the typesetting of math material, you may want to study Chapter 3 of Tobias Oetiker's "Not So Short Introduction to LaTeX2e".
By default the subscript uses \scriptstyle, so if you need a smaller subscript then use \scriptscriptstyle as shown in the given image below.
\documentclass[preview,border=12pt,12pt]{standalone}
\begin{document}
$v_0$ or $v_{\scriptstyle 0}$ or $v_{\scriptscriptstyle 0}$
\end{document}

$v_{0}$? Reading a basic guide is recommended; go to http://ctan.org and typelshortin the search box, you'll get a list of a good introductory guide in several languages. – egreg Oct 26 '13 at 19:36