How to disable automatic indentation on new paragraphs?

You can avoid the paragraph indention for specific paragraphs with the \noindent macro. If you want to disable it globally you could use \setlength{\parindent}{0pt}. However, I would not recommend changing it globally in your case, because that's effectively changes the template, even if the actual file isn't modified.

The parskip package turns off the indentation and adds a little bit of (stretchable) space in between paragraphs. It might be an option if you don't mind the inter-paragraph spacing. Simply add \usepackage{parskip} to your preamble to use the package. Martin's last sentence applies to this solution as well, of course.

If you are working with a KOMA document class, I can also recommend to use the parskip=full option as it handles the spaces based on your wish to remove the paragraph indentation pretty well (adds vertical spacing between paragraphs, etc.).

Example: \documentclass[parskip=full]{scrreprt}.