Where you place the microphone and the type of microphone you use when recording dialogue has a substantial effect on the quality of the automatic dialogue replacement. There are many different microphones capable of handling the work. Although shotgun microphones, boom microphones and lavaliere microphones are common, the one you select depends on the microphones used in the original shoot and the sound you are trying to mix. In order to capture sound matching the original ambient environment, the mixer needs to listen through headphones to determine the exact type and combination of microphones as well as how far the actor or actors should stand in relationship to the microphone.
Part of the process is working with actors to ensure they reproduce the correct inflections as well as getting the recorded sound to match the movement of their lips. It's often necessary to include the director to coach the actors. The mixer needs to make the actors comfortable, so they give a proper performance. Cues must also be given to the actor to ensure correct syncing. The cue is either a visual reference showing the actor's original performance on a monitor, or an audio reference playing the original dialogue into a headset worn by the actor. By setting up a reference, you'll ensure the new recording matches the actor's original performance.
For proper dialogue replacement audio is typically recorded in a sound studio or on a sound stage. This is because microphones are extremely sensitive and they often pick up sounds unnoticed by the naked ear and turn them into static or overpowering ambient noise that makes the dialogue unintelligible. By recording in a soundproof environment, you bypass this potential problem. It's also common to record dialogue replacement in a room with a computer. By plugging the microphone directly into a computer with built-in sound mixing software you save time. This is because the audio is recorded directly into a format the editor can use, rather than into a format that needs to be converted and imported.
If you're shooting on a shoestring budget, chances are you won't have access to a full studio or sound stage. However, you can still record dialogue replacement for your independent film. All you need is a computer, a microphone, audio recording software, a windscreen and your actors. When you record this way, you'll need plenty of time to make sure that you capture the sound quality you desire. Keep in mind you don't have to replace all dialogue, only the unusable portions. You can even record sections of dialogue instead of entire speeches, provided you are able to match the sound quality between the clips.