Well, if you know what kind of pickups you have you can simply look up the manufacterer specs and the internet. They should tell the output levels, the resitance levels, inductance, along with what type of magnet they used. Sometimes you can tell just by listening to the tone of the pickups at a clean level. Like I said the Alnico 2 is brighter, the 5 is warmer and the Ceramics are slightly brighter with a touch of natural overdrive. But they can get tricky because they use the different overwound/underwound techniques to get varied tone... such as... The Texas Special Fender pickups are nothing more than an over wound Alnico 5. This gives it it's fat, yet biting tone. And if you heard them you would probably think they're either a ceramic or Alnico 2... But if you played an overwound Alnico 5 next to a standard wound Alnico 2, they will still sound different. So this is where pickup companies and guitar companies get the varied tones in their pickups. Just look around for what type of pickups are in your guitar and then try to find the specs for those pickups. They shouldn't be hard to find.