How exactly are families and genera distinguished?

Trolling through the WSC, as far as I can tell the sole describer for genera seems to be similar sexual characteristics, with species designation given by exact same sexual characteristics (which makes sense). However, I am completely new to taxonomic classification, and while I intend to pursue a zoology/biosciences degree in the near future, I don't want to be leading myself astray while researching spiders on my own. TIA!