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Sure!
They have half your hitpoints.
They treat your level as their hit dice for effects related to hit dice (think color spray or sleep) unless theirs is better.
They use your base saves and base attack bonus unless theirs is better.
They use your skill ranks (unless theirs are better) but their own ability modifiers.
They get special abilities as per the familiar ability table based on your spellcaster level.
So... Basically the same way you advance a normal familiar.
Edit: LINK (Familiar Ability Descriptions is a few down from there.)