a. What is needed for effective quality recording? It would be wonderful to have a sound studio to record in with echo-resistant walls and total quiet from any and all extraneous noises. Look for the best quiet facility you can locate for placing your computer and mike. You can add various types of sound suppressant materials if you wish and Rudolph/Leonard mention many ways a studio can be developed within a private house.
I have had some problems with bleed through from my earphone when using a headset with a mike attached. However, I find that I can listen to what is being played back from the computer through my head set and while playing/recording into the desk mike. This reduces the bleed through factor. As my recorder is within a foot of the mike (called "tight" mic placement) , I can successfully record decent tracks even though I have had pretty constant noise in the rooms around my computer. A noise factor in the fan motor on the computer.
An Excellent Text for Reading by Anyone Interested in Working with Digital Audio in Music Technology!
Tom Rudolph, in his book Recording in the Digital World mentions ways of distancing the computer from your recording area. He mentions the Gefen TSE connectivity products which allows the CPU to be 500 or more feet away from the monitor, keyboard, and mouse. Fortunately, my mic seems to factor most noise out. However, I can still see some fan noise in my mixer window in my files.
b. Simple microphones such as the Labtec AM-242 incorporate anti-noise reduction that will provide directional support without having background noise amplified. Labtec mics feature special noise canceling technology and are condenser-type microphones that work very well in close proximity to the recording source. Since much room noise is excluded by the NCAT (Noise Canceling Amplification Technology), recording in a relatively quiet room is a possibility. Microphone response 100-16,000 Hz .Sensitivity -58 dBV/uBar, -38 dBV/Pa +/-4dB, Off-axis Noise Cancelling: -30db @ 250 Hz.