Stat write-ups for regular and improved familiars both post total bonuses, but it's the individual ranks that the spellcaster needs to know.
[Edit] - And if a familiar doesn't have ranks in one of it's "class" skills, but the caster does (such as Fly) does the familiar, when using the Caster's ranks instead of it's own, gain the +3 class skill bonus?
The easiest way is to use a program like Hero Lab.
To do it by hand:
1) Subtract ability score modifiers, racial modifiers, movement type modifiers (to Climb, Fly, and/or Swim), and any feat-granted modifiers from all listed skills.
2) Subtract +3 bonus for any trained class skills (determined by creature type; check the back of the Bestiary for lists)
As a rule of thumb, if the familiar is an animal, it should have a total number of skill ranks equal to its Hit Dice. Most animals will only have one or two trained skills, so if one skill looks particularly beefy, reverse-engineer its ranks first; you'll probably be done at that point.
@John - I think the problem is that Improved Familiar grants so many harder to manage options. As you can see in my post above, my familiar is an Outsider, so it's not "set-in-stone" stats like an Animal type would have. :\
Thanks for the quick reply though!