VSE - How do I fade or trim an image and audio?

I have been reading about the Video Sequence Editor on the Blender wiki and I can’t find an answer to this question.

I have a movie strip and above it I have a black image. I want to fade the black image so it fades into the movie clip so I selected the image and used an “alpha over” and just keyframed the opacity. Is this the correct way to do this?

How do I fade or trim an audio track?
Also is it possible to fade or trim an audio track so the sound fades at the end for example?

Any ideas what “Alpha Under” and “Overdrop” do?

Leave the opacity alone, and just select the black image, then shift-select the movie clip, then add a Gamma Cross strip from the Effect category.

To make the audio fade find it’s Volume number. Hover your cursor over it and press ‘i’ to set a keyframe. Set it to zero when you want it to be out, and 1 when you want it to be full volume.