<p>Selecting a large amount of text that extends over many screens in an IDE like Eclipse is fairly easy since you can use the mouse, but what is the best way to e.g. select and delete multiscreen blocks of text or write e.g. three large methods out to another file and then delete them for testing purposes in Vim when using it via putty/ssh where you cannot use the mouse?</p>

<p>I can easily yank-to-the-end-of-line or yank-to-the-end-of-code-block but if the text extends over many screens, or has lots of blank lines in it, I feel like my hands are tied in Vim. Any solutions?</p>

<p>And a related question: is there a way to somehow select 40 lines, and then comment them all out (with "#" or "//"), as is common in most IDEs?</p>

Use the visual block command v (or V for whole lines and
C
-
V
for rectangular blocks). While in visual block mode, you can use any motion commands including search; I use } frequently to skip to the next blank line. Once the block is marked, you can :w it to a file, delete, yank, or whatever. If you execute a command and the visual block goes away, re-select the same block with gv. See :help visual-change for more.
I think there are language-specific scripts that come with vim that do things like comment out blocks of code in a way that fits your language of choice.