Guitar pickups are one of the most important parts of your tone and there are literally hundreds of options available from different companies. In the following article we look at the possibilities and the challenges that await you.
1) First off, identify what type of guitar pickups you have.
Active: Such as EMG or Seymour Duncan Blackouts Guitar Pickups. You can easily change these out with another active pickup from either brand, but changing to passive will require a little more work and you will need 500K potentiometer and new jack.
Passive Humbucker: The humbucker is the most common pickup type out there. It was developed by Gibson and you can get almost any kind of tone out of it.
Single Coil (Strat or Tele): Single coil pickups have a very particular tone. In a Tele they produce a lot of Twang and can be either dark or screaming with output. Same goes for a Strat. The one setback for single-coils has been the hum, you certainly don't want to pickup your refrigrator or power lines as well as your guitar. There are many options like the stacked design from Seymour Duncan or humbuckers in a single-coil size.
P90: They have been described as somewhere between a single-coil and a humbucker, rude with an airy tone. Keep in mind there are two different sizes of P90: Soapbar and Dog Ear.
Mini-Humbuckers: mini humbuckers were popularly featured on the Firebird but now you may can find them on some Strats and Teles. Their tone is somewhere between a P90 and a humbucker. They aren't quite as raw as a P90 but have plenty of brightness and are quite a bit fatter than single-coils.
Once you have identified the type of pickup you want, the next thing you need to do is figure out what kind of tone you want. It helps to identify the exact qualities you want but if you just want to emulate an artists sound you can search on Google to see what pickups they used. Otherwise please see what terms on the below list apply to you:
Now that you know what you want, send an email to the following addresses describing what pickup type you have, what tone you want and what kind of music you play. Once you get a response, check out some demos on YouTube and see which sounds more like what you are looking for.
Bare Knuckle Pickups: https://bareknucklepickups.co.uk/ccs/open.php
Many of the pickup companies also have tools to help you identify the right kind of pickups you want:
Seymour Duncan: http://www.seymourduncan.com/support/tone-wizard/
Now that you have your set of pickups you have two options. You can either put them in yourself or pay a luthier around $40-$50 to put them in for you. If you have used a soldering iron before or don't feel intimidated I would encourage you to go ahead and install them; assuming you aren't trying to do any fancy Jimmy Page wiring.
If you need specialized or custom guitar pickups here are a couple popular options: