Adjusting volume when connected to stereo system

I have volunteered to provide the music for my friend’s party next week. The music will be MP3 files that will be played on my Sansa Clip+, which will be connected to my friend’s stereo system. I’m wondering which method I should use to adjust the volume during the party. Would it be best to use the volume control on the Sansa or the volume control on the stereo system?

For a party it makes no difference. For something like making high quality recordings, you would max out the players volume first.