A french drain is usually made up of stone or gravel in a ditch that redirects water (no pipe). If you want to use a pipe in the ditch make sure the perforations are up to collect the water and the smooth side is down to drain the water away.
Also make sure you use stone to stop dirt from entering the perforations. You can also use a pipe that id perforated that also has a sock on the outside.
When digging your trench make sure you dig it with a slope usually it is one foot drop for every 100 feet i.e: if your run is 50 feet it should be 6" lower at the end of the run.