Hi,
This is more about microphone type and positioning than recorder settings.
To maximise the voice and minimise the background:
Mono hypercardoid or perhaps cardoid mic.
Or use the a simple mono electret such as the one that probably came with your player (depending on which player you have).
Point mic
directly  at speaker.
Have mic
close to speaker (but not so close as to have 'popping' on Ps and Bs during speach.)
Set levels so that during loudest speaking, Â the bars almost, but not quite reach 0db maximum.
That's the short version.
And close the windows and tell the audience to shut up.
There's a very good recording guide by a guy called Framesaver on the mysticriver forums.
I'm not sure it would be good form for me to link to it here, but you should be able to find it.
Note the guide refers to iRivers with iRiver firmware, but most things apply.