I generally start mine once every two weeks out of a month but once a month should suffice. When you start it let it idle for about eight/ten minutes, and let the A/C run for about five mins to keep the compressor lubricated (if you got Air cond). Oh yea if you are not jacking it don't leave the e-brake on just park it in gear or P, this will keep the back brakes from seizing.
Do you have an engine block heater? Use it before you start it, otherwise try and start it on a reasonably mild day or else this will not work well. Cold temps mean longer idle times to get the oil moving. With all the mods you have you def want to keep it working properly.
Good luck