2. How do I make a copy of the screen (screenshot)?

Focus

Make sure the window you want a screenshot from is active/focussed.

Send screen to copy-buffer

By pressing ALT+PrtScn (PrtScn is usually the key above 'insert') you copy an image of the screen to the copy-paste buffer. Note: On most laptops you need to use the FN (Function) key in combination with PrtScn (/insert).

Paste the picture in a graphic program

Open any graphic program (e.g. Ms-Paint, Photoshop, PaintShop) and select 'paste' from the edit menu (in Photoshop, use CTRL-N to create a new picture first).

Save the picture as JPG

Save the picture as jpg/jpeg. The default is BMP which is quite sucky because it doesn't compress. A BMP file of several Megabytes will only be a few Kilobytes as a JPG!

Screenshot on Apple Mac

Focus

Make sure the window you want a screenshot from is active/focussed.

Making an image file of a section of the sceen

Press shift, command 4 and your cursor will turn into a lasso tool. Click and drag around the area you want and let go. A file will be saved to your desktop called 'Picture 1.png' (number increments for every file).

Convert to JPG

Open any graphic program (e.g. Ms-Paint, Photoshop, Paintshop, GraphicConverter), open the file 'picture 1.png' and save the picture as JPG. Depending on the size of your screen you may want to reduce the number of pixels (resulution) to reduce the file size.