The reason for the vertical space is the default margins. I would recommend using the geometry package for changing the page geometry.
With the [showframe] option to the geometry package you see that the text is actually already at the top of the page, but the page has a margin before the text starts (The gray bar at the top is the top of the page):

To see which dimensions you need to adjust you can use \layout from the layout package. So, with the following:
\documentclass{article}
\usepackage[showframe]{geometry}
\usepackage{layout}
\begin{document}\layout
Hello there.
\end{document}
you get a nice image on page 1 that shows the various dimensions. From the top of this page you see:

So the dimensions you are interested in are (2) and (6). From the bottom of the page we see:

Hence you need to adjust \voffset and \headsep.
Since 1.0in is added to the dimension specified in \voffset, I set that to a negative value.
So, for instance setting this to:
\setlength{\voffset}{-0.75in}
\setlength{\headsep}{5pt}
you achieve:

Code:
\documentclass{article}
\usepackage[showframe]{geometry}
%\usepackage{layout}
\setlength{\voffset}{-0.75in}
\setlength{\headsep}{5pt}
\begin{document}%\layout
Hello there.
\end{document}
\documentclassand packages. I'd suggest you post a new question that with a MWE including\documentclassand the appropriate packages that reproduce the problem. If it is relevant you can reference this question in your post. – Peter Grill Nov 08 '15 at 10:34