Entering Query Conditions in Standard Forms

Recently i want to query on a stadard form for records having reversal date as null
i remember that i need to give is null but it didn't work...some how i manager to do it from backend..Even i searched developer guide with no use...So how i get this from the form guide and i am publishing for easy reference..these things will be very useful..and makes our life easy..

1. to enter query by example
2. to recall the last query parameters
3. to Execute Query
4. Query : Count Matching Records (after putting in the query parameters)

Query Wild Card Characters
% one or more characters
_ exactly one character

Query Operators
#between and --need to give #
#is null
#is not null
> Greater Than
>= Greater Than or Equal
< Less Than
<= Less Than or Equal
= Equal
!= Not Equal