Ensure that the vocalist is standing far enough away from the microphone to provide a clear sound without static. A good number is six to eight inches away from the microphone. Other considerations should include how the vocalist is dressed. They should be dressed in cotton clothing that won't rattle or make noise while speaking. Tennis shoes should be worn to prevent hearing footsteps and the vocalist should be instructed to move as little as possible.
Thuds and footsteps are going to happen in a dubbing session. Rather than throw out the whole session, set a high-pass filter to cut anything under 65 hertz. These filters will not completely remove all sound, but they will greatly reduce it and in many cases eliminate static, footsteps and low frequency noises. You can also use a low-pass filter to remove higher pitched frequencies that may have been introduced into a recording. Start by setting the low-pass filter to 1200 hertz and then lower it gradually if the recording has not been improved.
While the vocalist is speaking, he should be able to monitor the video to try to line up the speech patterns with the movements of the characters mouth. An ideal situation involves the vocals being recorded first and then the video. However, it is often necessary to create a dub after the video has already been created. For example, when translating between languages, the speaker will have to try to match the movements of the mouth as much as possible.
The microphone should be a unidirectional cardioid mic. This type of mic has a heart-shaped pattern that creates a warm sound and is excellent for recording vocals. Direct the microphone just below the speaker's mouth for the greatest effect. Choosing an omnidirectional or bidirectional mic will cause problems with the final sound quality and will pick up additional artifacts not intended. Place the microphone on a stand so that the speaker does not have to fidget with the microphone. You also may wish to install a wind guard on the front of the mic to avoid catching any hissing or spitting noise.