Help on any Unix command. RTFM!
man {command}Type man ls to read the manual for the ls command.
man {command} > {filename}Redirect help to a file to download.
whatis {command}Give short description of command.
apropos {keyword}Search for all Unix commands that match keyword, eg apropos file

List a directory
ls {path}It's ok to combine attributes, eg ls -laF gets a long listing of all files with types.
ls {path_1} {path_2}List both {path_1} and {path_2}.
ls -l {path}Long listing, with date, size and permisions.
ls -a {path}Show all files, including important .dot files that don't otherwise show.
ls -F {path}Show type of each file. "/" = directory, "*" = executable.
ls -R {path}Recursive listing, with all subdirs.
ls {path} > {filename}Redirect directory to a file.
ls {path} | moreShow listing one screen at a time.
dir {path}Useful alias for DOS people, or use with ncftp.

Change to directory
cd {dirname}There must be a space between.
cd ~Go back to home directory, useful if you're lost.
cd ..Go back one directory.
cdupUseful alias, like "cd ..", or use with ncftp.

Make a new directory
mkdir {dirname}

Remove a directory
rmdir {dirname}Only works if {dirname} is empty.
rm -r {dirname}Remove all files and subdirs. Careful!

Print working directory
pwdShow where you are as full path. Useful if you're lost or exploring.

Copy a file or directory
cp {file1} {file2}
cp -r {dir1} {dir2}Recursive, copy directory and all subdirs.
cat {newfile} >> {oldfile}Append newfile to end of oldfile.

Move (or rename) a file
mv {oldfile} {newfile}Moving a file and renaming it are the same thing.
mv {oldname} {newname}

Delete a file
rm {filespec}? and * wildcards work like DOS should. "?" is any character; "*" is any string of characters.
ls {filespec}
rm {filespec}
Good strategy: first list a group to make sure it's what's you think...
...then delete it all at once.

View a text file
more {filename}View file one screen at a time.
less {filename}Like more, with extra features.
cat {filename}View file, but it scrolls.
cat {filename} | moreView file one screen at a time.
page {filename}Very handy with ncftp.
pico {filename}Use text editor and don't save.

Edit a text file.
pico {filename}The same editor PINE uses, so you already know it. vi and emacs are also available.

Create a text file.
cat > {filename}Enter your text (multiple lines with enter are ok) and press control-d to save.
pico {filename}Create some text and save it.

Compare two files
diff {file1} {file2}Show the differences.
sdiff {file1} {file2}Show files side by side.

Other text commands
grep '{pattern}' {file}Find regular expression in file.
sort {file1} > {file2}Sort file1 and save as file2.
sort -o {file} {file}Replace file with sorted version.
spell {file}Display misspelled words.
wc {file}Count words in file.

Find files on system
find {filespec}Works with wildcards. Handy for snooping.
find {filespec} > {filename}Redirect find list to file. Can be big!

Make an Alias
alias {name} '{command}'Put the command in 'single quotes'. More useful in your .cshrc file.

Wildcards and Shortcuts
*Match any string of characters, eg page* gets page1, page10, and page.txt.
?Match any single character, eg page? gets page1 and page2, but not page10.
[...]Match any characters in a range, eg page[1-3] gets page1, page2, and page3.
~Short for your home directory, eg cd ~ will take you home, and rm -r ~ will destroy it.
.The current directory.
..One directory up the tree, eg ls ...

Pipes and Redirection(You pipe a command to another command, and redirect it to a file.)
{command} > {file}Redirect output to a file, eg ls > list.txt writes directory to file.
{command} >> {file}Append output to an existing file, eg cat update >> archive adds update to end of archive.
{command} < {file}Get input from a file, eg sort < file.txt
{command} < {file1} > {file2}Get input from file1, and write to file2, eg sort < old.txt > new.txt sorts old.txt and saves as new.txt.
{command} | {command}Pipe one command to another, eg ls | more gets directory and sends it to more to show it one page at a time.

Permissions, important and tricky!
Unix permissions concern who can read a file or directory, write to it, and execute it. Permissions are granted or withheld with a magic 3-digit number. The three digits correspond to the owner (you); the group (?); and the world (everyone else).

Think of each digit as a sum:

execute permission = 1
write permission = 2
write and execute (1+2)= 3
read permission = 4
read and execute (4+1)= 5
read and write (4+2)= 6
read, write and execute (4+2+1)= 7

Add the number value of the permissions you want to grant each group to make a three digit number, one digit each for the owner, the group, and the world. Here are some useful combinations. Try to figure them out!

chmod 600 {filespec}You can read and write; the world can't. Good for files.
chmod 700 {filespec}You can read, write, and execute; the world can't. Good for scripts.
chmod 644 {filespec}You can read and write; the world can only read. Good for web pages.
chmod 755 {filespec}You can read, write, and execute; the world can read and execute. Good for programs you want to share, and your public_html directory.

Permissions, another way
You can also change file permissions with letters:

u = user (yourself) g = group a = everyone
r = read w = write x = execute

chmod u+rw {filespec}Give yourself read and write permission
chmod u+x {filespec}Give yourself execute permission.
chmod a+rw {filespec}Give read and write permission to everyone.

Useful apps
lynxText-based Web browser, fast and lean.
ncftpBetter FTP.
pico {filename}Easy text editor, but limited. vi and emacs are available.
wget {url}Download the interweb

System info
dateShow date and time.
dfCheck system disk capacity.
duCheck your disk usage and show bytes in each directory.
more /etc/motdRead message of the day, "motd" is a useful alias..
printenvShow all environmental variables (in C-shell% - use set in Korn shell$).
quota -vCheck your total disk use.
uptimeFind out system load.
wWho's online and what are they doing?