"Put the playhead on the shot you want, hit "x" to mark that shot"
this should put in and out points around your shot,
but is dependant on a few conditions being met for it to work properly,
so just check that before you export.
anohter way to do this is to double click on the shot in question,
opening it into the viewer,
and export from there.
that will export the clip with it's native settings,
exporting from the timeline wil export with the TIMELINE settings
most likely thay are the same.
another bit of techno trivia:
exporting from the viewer will keep the clip's TC,
exporting from the timeline will give the export the TC of the timeline.
nick