SQL*Plus executables:
sqlplusw (Windows only)
sqlplus  (UNIX and Windows)

Logging in to SQL*Plus
via windows, dos or unix

SQL*Plus Windows shortcut
Right click on icon to get Properties:
target - this indicates the sqlplus exe you want to use
C:\Oracle\Ora81\bin\SQLPLUSW.EXE

you can extend the functionality of target by adding your username and database name
C:\Oracle\Ora81\bin\SQLPLUSW.EXE username@mydatabase

or adding name, password and database name(MAKE SURE YOUR PC IS SECURE AT ALL TIMES!!)
C:\Oracle\Ora81\bin\SQLPLUSW.EXE password/username@mydatabase 

and you can even automatically call a script that resides in your 'start in' directory
C:\Oracle\Ora81\bin\SQLPLUSW.EXE password/username@mydatabase @ulcase1.sql

or you can automatically call a script by specifying the full path of the script
C:\Oracle\Ora81\bin\SQLPLUSW.EXE password/username@mydatabase @c:\\ulcase1.sql

start in  - use to set your current directory where your scripts are stored

You can also set up a shortcut key to invoke the shortcut, indicate if you want sqlplusw to run in a normal, full or minimized window with run and give a comment for mouse-over help.

Also, you can change the text of the icon indicating the shortcut to help you remember how you set up the shortcut.

Executing SQL
A few examples:
select
select *
from emp;

insert
insert into dept (deptno, dname, loc)
values(80, 'IT', 'Boston');

update
update dept
set loc = 'Madison'
where deptno = 80;

delete
delete dept
where deptno = 80;

commit
commit; -- allows you to make your insert, update or delete changes permanent

rollback
rollback; -- allows you to undo your insert, update and delete statements since the last commit

Sending output to a file (spooling to a file)
log in to the database using SQL*Plus
SQL> spool test.out
SQL> select * from emp;
SQL> spool off
SQL> edit test.out

Running SQL*Plus scripts (scripts can contain both SQL*Plus commands and SQL statements)
Using the '@':
SQL> @ulcase1.sql  (script must be in your 'current' directory)
or
SQL> @c:\path\ulcase1.sql (indicate full path so your current directory doesn't matter

or using the start command:
SQL> start ulcase1.sql

Each SQL statement in your script must end in a ';' or a '/'.

A special 'script' called the buffer (seen on the OS as afiedt.buf)
The buffer stores the last SQL statement that was executed.  The buffer holds only SQL statements. 
Too see the contents of the buffer:
SQL> edit
or 
SQL> list

To change the contents of the buffer:
run a new SQL statement
or 
SQL> edit 
or 
use sqlplus line mode edit commands - see page 46 and 47 of the SQL*Plus User Guide or attached printout of those pages.

What's the deal with the '/'?
The '/' is the sqlplus run command.  The buffer needs to end in the '/' to run.  The '/' can be used to re-execute the command in the buffer.  The ';' is not allowed in the buffer but is allowed in any other sqlplus script.

Try this:
SQL> select * from emp;
SQL> /
The second line will run the statement in the buffer which is the last statement you ran.

Comments
-- single line
or 
/* 
  multiple line
*/


SQL*Plus commands vs SQL statements
SQL*Plus commands are used to affect the SQL*Plus environment and are proprietary to SQL*Plus.
SQL statements are used to affect the database or get information from the database and can be executed from any tool that supports SQL.

SQL*Plus commands do not end in a ';' or '/'.

Examples of SQL*Plus commands we have seen so far:
@
/
start
list
edit
spool

The save command will save the contents of the buffer to a file in the current directory:
SQL> select * from emp;
SQL> save test.sql
This will save 'select * from emp' to the file test.sql

Changing the behavior of your SQL*Plus session using the SQL*Plus command set:
set linesize 500
set echo on
set echo off
set pagesize 80

There are many more set options.  These can be seen either in the documentation or in sqlplusw from the menu Options|Environment.

The show command allows you to see who what user id you are using:
SQL> show user

The column command can be useful for formatting results from a query (select statement):
SQL> column <column name> format a10
this formats any column with <column name> for a heading as an alpha-numeric width of 10.

SQL> column <column name> format $99,999.99
  this formats any column with <column name> for a heading as currency.

The describe command allows you to see the structure of a table:
SQL> desc emp
 Name                          Null?    Type
 ----------------------------- -------- --------------------
 EMPNO                         NOT NULL NUMBER(4)
 ENAME                                  CHAR(10)
 JOB                                    CHAR(9)
 MGR                                    NUMBER(4)
 HIREDATE                               DATE
 SAL                                    NUMBER(7,2)
 COMM                                   NUMBER(7,2)
 DEPTNO                                 NUMBER(2)

The exit command allows you to end your SQL*Plus session.  It also can be embedded in a script to automatically exit SQL*Plus at the end of the script.