What guitars do you have? Or more specifically, is it humbucker or single coil pickup?
Single coils will often hum. Personally I have noiseless Kinman pickups in almost all my single coil guitars (4 Stratocasters and 1 Tele). That doesn't remove all the hum, so I have also treated my guitars with copper foil as shielding inside the relevant cavities. You can buy this stuff as selfadhessive tape: www.stewmac.com
And for shielding advice try www.guitarnuts.com
You may also find good advice at www.kinman.com
You can have sources of noise in your studio. Fluorescent lamps will generate electrical noise. Televisions, radios and other electronic things may too.
One method I have used with much succes is to just ground the guitar with a wire. Attach a wire to a radiator or some other plumbing tube or other metal that gives you a good ground. Use a long wire and attach the other end to the guitar. I usually have one of those crocodile things which can be attached to one of the tuners (if they are metallic). Otherwise find elsewher on the guitar to attach it, so that the guitar is connected to ground all the time.
The ground wire makes a huge difference, and you get rid of that click whenever touching the guitar. Actually just touching the guitar removes a lot of hum too, but while playing you can't make sure you touch the strings all the time, and letting go immediately gives a hum. Particularly if you use compression in the chain. That's why the ground wire works so fine.