Download and install an audio editor and/or mixer to your computer hard drive; the software you download should be capable of slicing and mixing audio as well as importing all types of sound files such as mp3 and wav. Another characteristic of good audio editor software is the ability to pull audio from .mov or .mpeg files, which is important for creating movie sound bites. An example of such an audio editor software is Audacity, a free open source audio editor that can be used in Windows, Linux and Mac platforms.
Open the audio editing software to get started making movie sound bites. Import and convert movie files to the software to editable formats such as mp3 or wav if you don't already have audio track files from the movie. Follow the specific instructions or user help guide for the particular editing software to accomplish this; refer to the software publisher's site if necessary.
Find and cut the movie audio section from which you'd like to make the sound bite. Use the audio editing program's selection and/or time delimiting tools to highlight the areas which you'd like to edit and make into a sound bite. Many audio editors contain trimming and splitting tools to make this happen. For example, in the open source software Audacity you can select and cut all the areas which you'd like to remove, or you can cut the specific audio section and create a new project consisting of only the cut audio.
Edit the sound clip further by refining the pitch, tone or sound level. Many audio editing programs allow you to edit with specific tools such as mute buttons, drawing and zooming tools to edit individual sound samples, and echo effects. Refer to the user guide of the editing software for help or instructions.
Save the movie sound bite as a new project in the audio editing program or export the sound clip as an audio file if you've finished editing. The majority of such programs allows you to export movie sound bites and clips to audio mp3 and/or wav files.