There are two main system tables which give you such information:

• dbo.sysobjects
• dbo.syscolumns

Example below shows how to gather column list for specified table.

DECLARE
  @TABLENAME varchar(256),
  @COLUMNS varchar(4000)
SET @TABLENAME = 'mytable'
SET @COLUMNS = ''
SELECT @COLUMNS = @COLUMNS + c.name + ', '
FROM syscolumns c
INNER JOIN sysobjects o ON o.id = c.id
WHERE o.name = @TABLENAME AND o.xtype='U'
ORDER BY colid
SET @COLUMNS = SUBSTRING(@COLUMNS, 1, Datalength(@COLUMNS) - 2)
SELECT @COLUMNS

or if you prefer more generic approach

DECLARE
  @TABLENAME varchar(256),
  @COLUMNS varchar(4000)
SET @TABLENAME = 'mytable'
SET @COLUMNS = ''
SET @COLUMNS = ''
SELECT @COLUMNS = @COLUMNS + COLUMN_NAME + ', '
FROM INFORMATION_SCHEMA.Columns
WHERE TABLE_NAME = @TABLENAME
ORDER BY ORDINAL_POSITION
SET @COLUMNS = SUBSTRING(@COLUMNS, 1, Datalength(@COLUMNS) - 2)
SELECT @COLUMNS

Result is a coma-separated list of columns in the table in order they appear.

Note. Check for xtype in the first example could be useful but not required, since you probably do not mix table name with any other object names. Otherwise, it would be necessary to ensure that you are looking at the table and not something else.
Other possible values for this column are:

• S – System tables
• U – User table
• TR – Triggers
• P – Stored procedure
• RF – Replication filter stored procedure
• X – Extended stored procedure
• V – View
• TF – Functions
• C – CHECK constraint
• D – DEFAULT constraint
• F – FOREIGN KEY constraint
• PK – PRIMARY KEY constraint (type is K)
• UQ – UNIQUE constraint (type is K)
• L – Log