Below are some of the more common UNIX commands. NOTE: When you remove a UNIX file, it's really gone!! There is no wastebasket or recycling bin, and it does not maintain versions of files!! (The emacs editor, though, always keeps a backup copy of a file you're editing.)

man keyword	the most important command, get's help on keyword which is usually a command. Also try:
man -k keyword	if you do not know the syntax of the command. Play around with these a bit.
make	execute a Makefile to compile files
cd directory	change to directory
cd ..	go up one level in the directory tree
cd /	go to root of directory tree
ls	list all files in the current directory
ls .*	check this out, those files are usually not listed
ls -l	to see statistics about your files
rm file	remove file
rm *	remove all files (go easy on that one)
cp file1 file2	copy file1 to file2 (keeps file1)
mv file1 file2	renames file1 to file2. Can also me used to move files in the directory tree.
mkdir directory	make a new subdirectory
rmdir directory	remove subdirectory
rm -r directory	removes files in and below subdirectory i.e. even files in its sub (sub..) directories
more file	show file, one screen at a time
head file	show first 10 lines of file
tail file	show last 10 lines of file
chmod 700 file	change access priviledges. 7 stands for read, write, execute priviledges. The first digit sets the rights for yourself, the next one for everyone in your group, the last one for everyone who has access to the computer on which the file is located.
passwd	to change your password
grep string *	searches all files in the current directory for occurrence of string
lpr -Pprintque file	print file to printque. No space between P and printque.
telnet machine	start remote session to machine
ftp machine	if you want to transfer files between machines
get filename	when in FTP, used to copy a file FROM a remote machine
put filename	when in FTP, used to copy a file TO a remote machine
logout	logout