Hmmm, first of all you have to get familiar with your editing program and not be afraid to experiment with the effects etc.
Try to play around with some footage for awhile before you get serious about editing.
Once you know the basics then here are all tips I can give you:
-Try to synchronize music and scenes as much as possible
-Don't spam your videos with effects
-Take your time to choose your song
-Take your time to edit
I would have given you more tips but I don't know what kind of AMVs you want to specialize in (trailers or actual AMVs).
i'm also an editor, not so well-known but I like to think that my videos are in the least enjoyable.
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