Creativity is really important here and having done my first mash-up video, I understand how hard it is to accomplish a sync between the video clips and the sound track. The creation of an AMV centers on using various video editing techniques to create a feeling of synchronization and unity. Several techniques are available to achieve this:
1. Editing: Using different clips from the video source and changing between them at specific times is the most important tool the AMV creator has. Often both the events in the video and the transitions between the clips are synchronized with events in the music. The following is "Falling Again" from one of my favorite bands - Lacuna Coil - made with clips from Samurai X.
2. Digital effects: Using video editing software the video source can be modified in various ways. Some effects are designed to be imperceptible (such as modifying a scene to stop a character's mouth from moving) whereas others are intended to increase synchronism with the audio, or possibly create a unique visual style for the video. The first video below is a hilarious one with some great comdians featured with anime clips followed by "With You" from Linkin Park to the video clips of Bleach.
3. Lip-sync: the synchronization of the lip movements of a character in the original video source to the lyrics of the audio, to make it appear as if the character were singing the song. Lip-syncing is also commonly used in parody AMVs. These are created to poke fun at the characters in the anime that is being used. One very popular song in such AMVs is "If You Were Gay" from the Broadway musical Avenue Q made with clips from Gravitation.
4. Dimensions: Some editors use original and manipulated animation, both two-dimensional and three-dimensional, in AMV works. Such additions are often used for visual effect or to convey a story that is otherwise incommunicable using only the original video source. The following is a short video demonstrating how effects can be used to make simple clips look good together.
5. Keyframe manipulation and Dissolves: These are techniques in which the editor makes points in a video source on the timeline of the video editing program, that they can drag to different positions which makes the video either fade in or fade out. This can be to another video clip, or to a different color, most commonly solid black or solid white. Some of the best AMVs encompassing all these techniques can be found in this compilation video - which is about an hour long.
Many AMV editors submit their works to YouTube as it allows for straightforward uploading and viewing process. Due to the popularity and large user base of the site, YouTube is an option for an editor whose goal is heavy non-traditional AMV viewership and wide proliferation of their work. However, some creators have expressed an aversion to using the site to host their works due to the high level of video stream compression applied by YouTube. Also due to copyright laws, AMV's are no longer allowed on Youtube. As of December 1, 2007 all AMVs on YouTube will be deleted and any future uploads beyond December 1 will be rejected. So, watch them while you can!