[Jeff Hinkle]

In your After Effects Preferences, check out the Audio Hardware and Audio Output Mapping section. If you have your computer set to send all audio to the headphones, changing these two to System Default should send all your audio to your ‘phones.

—
It is easier to destroy than to create.
More fun, too.

[Jeff Hinkle]

By “colored blocks” do you mean color bars, like you see on TV accompanied by a test tone? That means After Effects has lost the link to your elements.

When you import something into AE, you don’t actually bring the items into the program; you just create a link to the files stored on your hard drive, external drive, what have you. If you move (or remove) those files, AE can no longer find them and puts up a color-bar placeholder to let you know it can no longer show them. No need to rebuild the animation, though. Just relink the missing file (right-click on the missing file name in your Project window and choose Replace Footage… and select the appropriate file) and your footage should reappear with all your previous animation work intact.

—
It is easier to destroy than to create.
More fun, too.

[Jeff Hinkle]

There’s several ways to do this. I don’t have CS6 yet, but I imagine they haven’t changed this functionality much.

With both images open, drag the layer you want to copy from the Layers palette to the new document. If you’re using tabbed windows, select the layer in the Layers palette and then drag the layer from the image (NOT the palette) to the tab of the second document and wait for it to open. Then move your pointer into the new document and release the mouse. In either instance, if you hold Shift while dragging, the layer will center itself into the new document (if its pixel dimensions are different from the original) or place itself in the exact same position (if its pixel dimensions are identical to the original).

You can right-click the layer in the Layers palette, choose Duplicate Layer… and in the resulting dialog box, choose your new document from the Destination pop-up menu.

You can even do copy>paste, but I don’t recommend it. That’s a lot of data to have hogging up RAM you could be using for other things.

Good luck and welcome to Photoshop.

—
It is easier to destroy than to create.
More fun, too.

[Jeff Hinkle]

That is a puzzler. Sounds like you’re doing everything correctly. I guess a few basic troubleshooting questions:

How are you duplicating the layer to a new document? Dragging to the new doc or right-click>duplicate layer?

Which version of Photoshop are you running?

Mac or PC?

—
It is easier to destroy than to create.
More fun, too.

[Jeff Hinkle]

How are you doing your cropping? Actually using the Crop tool, or merely changing the canvas size? If you select a portion of the photo with the Crop tool, hit Return, then drag that to a new image, that portion should be all you see. If you just change Canvas Size, the image data outside of the active image area is still there and will carry over to the new image.

—
It is easier to destroy than to create.
More fun, too.

[Jeff Hinkle]

Are you rendering with a straight or premultiplied alpha channel?

—
It is easier to destroy than to create.
More fun, too.

[Jeff Hinkle]

[Emanuel Ach] “So, what do you do in those moments? Curse? Drink?”

Both, usually.

[Jeff Hinkle]

With your pen tool, click on the last open point of the path. (The pen icon will gain a small square-on-a-line in the lower right corner when you’re properly positioned.) Once you click you’ll reactivate the path and can continue drawing as normal.

[Jeff Hinkle]

Along the top of the window, next to the tools, while you have a shape tool selected, there are two buttons: one with a star, one with a sort of dotted-line-shape thing. The star will make the tool create a shape, while the DLS thing will make the tool create a mask.

[Jeff Hinkle]

If the background is constant and indistinct, and you have a clean plate from later in the shoot, you could layer your clean plate on top of the hair and use the pen tool to draw a feathered mask around the part you need to cover. If the hair is small/thin enough and your background isn’t too detailed, you might be able to get away with that. Hard to say without seeing the shot.

If your backgrounds simply won’t match, there’s always the tedious approach of using the clone stamp tool in After Effects, or opening your movie in Photoshop and stepping through the frames, using whichever retouch tools you’re most comfortable with. I’d suggest making your camera assistant do it. Good learning experience.