How to use reference (cross-links) by their names

There are many ways to do this, see e.g. here:
http://www.tex.ac.uk/cgi-bin/texfaq2html?label=nameref

The way that works for me is the nameref command from within hyperref package. One possible usage is:

\section*{foo}
\label{sec:foo}

...
\nameref{sec:foo}

How to refer to sections

Use \label to add label to a section and \ref to refer to it.

\section{Greetings}
\label{sec:greetings}
 
Hello!
 
\section{Referencing}
 
I greeted in section~\ref{sec:greetings}.

 see http://en.wikibooks.org/wiki/LaTeX/Labels_and_Cross-referencing for more detils

How to make references to equations

To have correct references of the same form to the equations use the \autoref{} command from within the hyperref package. This will also creat hyperlinks within the document into the referred equations.

How to use multiple .bib files

Bibtex files are countaining references. In some cases we would like to use multiple .bib files, these we can simple enumerate in the  \bibliography command
as

\bibliography{file1,file2}

where file1.bib and file2.bib contain the references