Choosing the best professional microphone is a matter of both personal preference and matching the mic's characteristics to the type of sound you want to capture. Certain types of microphones are better suited for recording vocals than instruments, for example. Others are more appropriate for live sound than studio recording. Regardless of the frequency response or cartridge type you choose, selecting the right microphone ultimately means finding whichever is the best microphone for you.
Your first consideration should be the microphone's pickup pattern. There are two kinds: omnidirectional, which picks up sound from all sides, and unidirectional, which picks up sound from only one direction. Mics with a cardioid (or "heart-shaped") pattern control feedback and reject ambient sound. This makes cardioid-type mics preferable for recording vocals and close miking of acoustic instruments. Because cardioid mics reject the sound that is behind the pickup, they reduce room noise and the "bleed" from other instruments in the same room.
Inside a professional microphone are cartridges, or transducers. The two most common types are dynamic and condenser. Typically used more for live performance sound applications, dynamic mics can stand up to rough handling and high volume levels without feedback or distortion. They do not require a separate power source. Condenser mics are generally preferred in a studio environment because the more sensitive diaphragm more accurately captures the high frequencies, and therefore produces a cleaner, truer sound. Condensers do require a phantom power supply or batteries, and they tend to be considerably more expensive than dynamic microphones.
By far the most commonly used dynamic microphones are the Shure SM57 and SM58 for live vocals and instrument miking. Shure's economical SM57 also provides surprisingly good results for the price on guitar amplifiers and snare drums in the recording studio. The industry standard condenser large-diaphragm vocal mics are unquestionably Neumann's U87 and U47, both known to have a distinctive upper-midrange presence boost and a warm, bass tone. Mics that are similar but cost less are the AKG C12, the RØDE NT1000, and Audio Technica's AT-4033a and AT-4047.
If you plan to record direct to computer, you'll need a high quality sound card in addition to a microphone. Because of impedance matching, a professional microphone will produce little to no sound when plugged into a standard computer sound card. A microphone amplifier and preamp are needed to boost the microphone's output levels. Recording engineers agree that investing in a good preamp invariably makes even a low-cost microphone sound much better than the results of running an expensive microphone through a cheap preamp.
As professional microphones can cost thousands of dollars, home recording studios on a limited budget often get by with only one high-quality microphone and supplement with various types of less expensive mics. Conceivably, if a single musician played all of the instruments on his or her own album, the same microphone could be used to overdub each individual track. When narrowing your choice to just one quality microphone, select a mic that complements the vocals, as this is nearly always the most important element to record well in a song. A large diaphragm condenser mic offers enough flexibility that it can also produce crystal clear recordings of guitars, pianos, horns, woodwinds, drums, and amplifiers.