Quickest way to generate the columns used in the ctl file

Select decode (column_id, 1, ' ', ' , ') ||
rpad (column_name, 33, ' ') ||
decode (data_type,
'VARCHAR2', 'CHAR NULLIF ('||column_name||'=BLANKS)',
'FLOAT', 'DECIMAL EXTERNAL NULLIF('||column_name||'=BLANKS)',
'NUMBER', decode (data_precision, 0,
'INTEGER EXTERNAL NULLIF ('||column_name||
'=BLANKS)', decode (data_scale, 0,
'INTEGER EXTERNAL NULLIF ('||
column_name||'=BLANKS)',
'DECIMAL EXTERNAL NULLIF ('||
column_name||'=BLANKS)')),
'DATE', 'DATE "mm/dd/yy" NULLIF ('||
column_name||'=BLANKS)', null)
from all_tab_columns
where table_name = upper ('$LOADTABLE')
and owner = upper ('$SCHEMA')
order by column_id;

Note:
1. In the $LOADTABLE pass the table to which you want to SQL the data
2. In the $SCHEMA pass the schema in which the table is located.