I have one video clip of me taken in my makeshift studio and another video clip of a morning blue sky. I'd like to overlay the clips to create a "ghost" effect so that you can see through me into the blue sky, like you would be able to see through a ghost. How can I accomplish this special effect?
Do you just want to make the entire clip semi-transparent? That's pretty easy.
Place the sunrise clip on one video track and the clip of you on a track directly above it. Then, with the track including the footage of you selected, go to Insert menu and select the option to add a Video Envelope.
You'll then see a dark blue horizontal line along the top of the selected video track. Draw this line down and it will make the video on that track transparent. Drag it halfway down for semi-transparency.
You can see a demo of how envelopes work in my free Basic Training tutorials along the left side of this page. http://Muvipix.com/vms11.php
Envelopes are brilliant for changing the transparency of a clip in varying degrees along the clip. However, if you just want a fixed transparency for one clip simply hover your mouse pointer at the top edge of the clip that you want to make semi-transparent and a hand labelled 'Opacity is 100%' appears. Holding the left button pull down and the opacity of the clip will reduce (it's transparency will increase). The whole clip will then be at the transparency chosen.