Mixer toolbar settings input/output & snap to

What are ideal settings for input & output volume on the upper right for recording?
Could not find directions for the snap to settings, selection start/end-length,audio position.
Am trying to fill up an 80 min CD thanks Bob

Setting input levels: http://manual.audacityteam.org/o/man/tutorial_selecting_your_input.html

Snap to: http://manual.audacityteam.org/o/man/selection_toolbar.html#snap

Copying tapes, LPs or minidiscs to CD: http://manual.audacityteam.org/o/man/tutorial_copying_tapes_lps_or_minidiscs_to_cd.html