I think what you're looking for is found in Picard under Options -> File Naming. From there you can set a formatting template based on Picard's scripting language and tag names. There is also general help information available for the options.
The format template that I generally use here is:
$if2(%albumartist%,%artist%)/$if($ne(%album%,),%album% /)$if($gt(%totaldiscs%,1),%discnumber%-,)$if($ne(%tracknumber%,),$num(%tracknumber%,2) %title%,%title%)$if($ne(%musicbrainz_artistid%,%musicbrainz_albumartistid%), [%artist%],)
This should all be entered on one line with no spaces other than between "%tracknumber%,2)" and "%title", and just before "[%artist%]".
Hope this helps.