To complete a |\ref| command, position yourself between the curly braces of a \ref command and press <F9>. For example, you can press <F9> just after \ref{ or after \ref{eqn:. Latex-Suite will search for \label's in all tex files in the current directory and display the results in two windows as desribed in section Latex-Suite completion example.
Any command which contains the pattern ref in it is treated as if it is a way to call \ref indirectly. Thus pressing <F9> after something like \pref{ will also search for \label's.
When you press <F9> after typing \ref{eqn: then Latex-Suite will only list \label's which begin with eqn: If you press <F9> after a simple \ref{, then Latex-Suite will list all \label's in all the tex files in the present directory.
By prefixing your labels with eqn:, fig: etc, you can easily filter out a lot of undesirable results.