stem, staff & barline thickness
In professionally engraved scores, stems, staves and barlines are progressively thicker. As for ledger lines, they should be thicker than staff lines so they are usually configured to the same thickness as barlines.
The following image depicts the relationship between each of these types of lines.
Achieving this result, however, will require adjusting a few of the defaults. Although opinions as to the perfect thickness of each of these lines may vary from engraver to engraver, the following settings are in harmony with professional standards and will serve you well.
In FINALE, go to Document Options and adjust the following settings:
> Thin Line Thickness — 4 EVPUs
Lines and Curves
> Line Thickness > Staff Lines — 3.2 EVPUs
> Ledger Lines > Thickness — 4 EVPUs
> Stem Line Thickness — 2.4 EVPUs
In SIBELIUS, the default settings for stems (0.1 space), ledger lines (0.16 space) and barlines (0.16 space) are OK but the settings for the Staff Line Width should be changed from the default 0.1 space to 0.13 space. (See Engraving Rules > Staves > Staff Design.)
Oh, and by the way, in large scores with very small staves, these lines are usually thinned.