[quote name='Zenitram' timestamp='1339015050' post='1682568']
How does one know if a pick-up is passive or active? Do they look differently? Have more wires sticking out of them? Etc.
[/quote]
There are so many permutations that there isn't a cut and dried test. For instance 'many' Warwick MEC pups require a battery to operate but some don't (it's the preamp that requires the juice); active Warwick basses generally have an active/passive push/pull pot BUT that doesn't strictly mean that the pups are passive. Take the battery out of your Warwick and try it in passive mode, if it works then your pups are passive ($$ basses are afaik passive pups, most others aren't, they require a battery to power the preamp in them).