How to order citations by appearance using BibTeX?

There are three good answers to this question.

• Use the unsrt bibliography style, if you're happy with its formatting otherwise
• Use the makebst (link) tool to design your own bibliography style

And my personal recommendation:

• Use the biblatex package (link). It's the most complete and flexible bibliography tool in the LaTeX world.

Using biblatex, you'd write something like

\documentclass[12pt]{article}
\usepackage[sorting=none]{biblatex}
\bibliography{journals,phd-references} % Where journals.bib and phd-references.bib are BibTeX databases
\begin{document}
\cite{robertson2007}
\cite{earnshaw1842}
\printbibliography
\end{document}

Change

\bibliographystyle{plain}

to

\bibliographystyle{ieeetr}

Then rebuild it a few times to replace the .aux and .bbl files that were made when you used the plain style.

Or simply delete the .aux and .bbl files and rebuild.

If you use MiKTeX you shouldn't need to download anything extra.

The best I came up with is using the unsrt style, which seems to be a tweaked plain style. i.e.

\bibliographystyle{unsrt}
\bibliography{bibliography}

However what if my style is not the default?