The usual command to ask for a help page on the command line is the word man followed by the name of the command you need help with. You can get started with man man. It might help you to remember this, if you realize it's short for "manual."
A lot of plain text documents about packages can be found in /usr/doc/packages in modern distributions. If you installed them, you can also usually find the FAQs and HOWTOs installed in respective directories there.
Some applications have their own built-in access to help files (even those are usually text stored in another file, which can be reached in other ways). For example, pressing F1 in vim, ? in lynx, or ctrl-H followed by a key in Emacs, will get you into their help system. These may be confusing to novices, though.
Many programs provide minimal help about their command-line interface if given the command-line option --help or -?. Even if these don't work, most give a usage message if they don't understand their command- line arguments. The GNU project has especially forwarded this idea. It's a good one; every programmer creating a small utility should have it self-documented at least this much.
Graphical interfaces such as tkman and tkinfo will help quite a bit because they know where to find these kinds of help files; you can use their menus to help you find what you need. The better ones may also have more complex search functions.
Some of the bigger distributions link their default web pages to HTML versions of the help files. They may also have a link to help directly from the menus in their default X Windowing setup. Therefore, it's wise to install the default window manager, even if you (or the friend helping you) have a preference for another one, and to explore its menus a bit.
Check the FAQ. (Oh, you already are. ) Somewhat more seriously, there is a Linux FAQ located at http://www.linuxdoc.org/FAQ/Linux-FAQ.html which you might find to be helpful.
For people who are very new to Linux, especially if they are also new to computing in general, it may be handy to pick up one of these basic Linux books to get started:
Mailing lists exist for almost every application of any note, as well as for the distributions. If you get curious about a subject, and don't mind a bit of extra mail, sign onto applicable mailing lists as a "lurker" -- that is, just to read, not particularly to post. At some point it will make enough sense that their FAQ will seem very readable, and then you'll be well versed enough to ask more specific questions coherently. Don't forget to keep the slice of mail that advises you how to leave the mailing list when you tire of it or learn what you needed to know.
You may be able to meet with a local Linux User Group, if your area has one. There seem to be more all the time -- if you think you may not have one nearby, check the local university or community college before giving up.
And of course, there's always good general resources, such as the Linux Gazette
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